Sample LSAT Critical Reasoning Section

Answered with Complete Explanation

1. Most consumers do not get much use out of the sports equipment they purchase. For example, seventeen percent of the adults in the United States own jogging shoes, but only forty-five percent of the owners jog more than once a year, and only seventeen percent jog more than once a week.
Which of the following, if true, casts most doubt on the claim that most consumers get little use out of the sports equipment they purchase?
(A) Joggers are most susceptible to sports injuries during the first six months in which they jog.
(B) Joggers often exaggerate the frequency with which they jog in surveys designed to elicit such information.
(C) Many consumers purchase jogging shoes for use in activities other than jogging.
(D) Consumers who take up jogging often purchase an athletic shoe that can be used in other sports.
(E) Joggers who jog more than once a week are often active participants in other sports as well.

Explanation: The claim that most consumers do not get much use out of the sports equipment they purchase is supported by the infrequency with which jogging shoes are used for jogging. This reasoning overlooks the possibility that jogging shoes are used for other purposes; thus, choice C is the best answer.
Because injured joggers are less likely to use their jogging shoes, choice A is inappropriate. If B is true, joggers use their jogging shoes even less than the study cited states. So choice B is inappropriate. Because the consumers and joggers mentioned in D and E respectively are most likely to be among those who frequently use sports equipment and whose existence the argument concedes, D and E are inappropriate.

2. It is true that it is against international law to sell plutonium to countries that do not yet have nuclear weapons. But if United States companies do not do so, companies in other countries will.
Which of the following is most like the argument above in its logical structure?
(A) It is true that it is against the police department’s policy to negotiate with kidnappers. But if the police want to prevent loss of life, they must negotiate in some cases.
(B) it is true that it is illegal to refuse to register for military service. But there is a long tradition in the United States of conscientious objection to serving in the armed forces.
(C) It is true that it is illegal for a government official to participate in a transaction in which there is an apparent conflict of interest. But if the facts are examined carefully, it will clearly be seen that there was no actual conflict of interest in the defendant’s case.
(D) It is true that it is against the law to burglarize people’s homes. But someone else certainly would have burglarized that house if the defendant had not done so first.
(E) It is true that company policy forbids supervisors to fire employees without two written warnings. But there have been many supervisors who have disobeyed this policy.

Explanation: The argument in the passage acknowledges that a certain action contravenes a law, but it presents an excuse for the action by presupposing that someone will inevitably break this law. Only choice D shares all these features, and is thus the best answer.
In Choice A, an excuse is presented for contravening a stated policy. However, unlike in the passage and choice D, there is no presupposition that the policy will inevitably be contravened. Similarly, choices B and E report that illegal activities have occurred, without presupposing that they inevitably will. Choice C describes a case as being one to which the law that is stated is inapplicable.

3. Extinction is a process that can depend on a variety of ecological, geographical, and physiological variables. These variables affect different species of organisms in different ways, and should, therefore, yield a random pattern of extinctions. However, the fossil record shows that extinction occurs in a surprisingly definite pattern, with many species vanishing at the same time.
Which of the following, if true, forms the best basis for at least a partial explanation of the patterned extinctions revealed by the fossil record?
(A) Major episodes of extinction can result from widespread environmental disturbances that affect numerous different species.
(B) Certain extinction episodes selectively affect organisms with particular sets of characteristics unique to their species.
(C) Some species become extinct because of accumulated gradual changes in their local environments.
(D) In geologically recent times, for which there is no fossil record, human intervention has changed the pattern of extinctions.
(E) Species that are widely dispersed are the least likely to become extinct.

Explanation: Choice A, the best answer, asserts that some environmental disturbances can be so widespread as to cause the extinction of numerous species. This fact helps to explain why the fossil record frequently shows many species becoming extinct at the same time, despite the variety of factors that can cause a species to become extinct.
None of the other choices explain how numerous extinctions could have occurred simultaneously in the past. Choice B explains why sometimes only a very limited range of species become extinct. Choice C explains how some individual species become extinct. Choice D explains why the modern period is unlike the period of the fossil record, and choice E states which species are least likely to become extinct.

4. Shelby Industries manufactures and sells the same gauges as Jones Industries. Employee wages account for forty percent of the cost of manufacturing gauges at both Shelby Industries and Jones Industries. Shelby Industries is seeking a competitive advantage over Jones Industries. Therefore, to promote this end, Shelby Industries should lower employee wages.

Which of the following, if true, would most weaken the argument above?
(A) Because they make a small number of precision instruments, gauge manufacturers cannot receive volume discounts on raw materials.
(B) Lowering wages would reduce the quality of employee work, and this reduced quality would lead to lowered sales.
(C) Jones Industries has taken away twenty percent of Shelby Industries’ business over the last year.
(D) Shelby Industries pays its employees, on average, ten percent more than does Jones Industries.
(E) Many people who work for manufacturing plants live in areas in which the manufacturing plant they work for is the only industry.

Explanation: According to choice B, the effect of lowering wages is to reduce quality sufficiently to reduce sales. This is a good reason to doubt that wage cuts would give Shelby Industries any competitive advantage, so choice B is the best answer.
Some of the other choices provide good reasons for, rather than against, lowering wages. Choice A implies that reducing the cost of raw materials is not possible, choice D indicates that Shelby Industries’ wages are relatively high, and choice E suggests that Shelby Industries would not lose many workers if it did reduce wages. Choice C gives a reason for Shelby Industries to be concerned about its competitive position but no reason to think wage cuts would not improve that position.

5. Large national budget deficits do not cause large trade deficits. If they did, countries with the largest budget deficits would also have the largest trade deficits. In fact, when deficit figures are adjusted so that different countries are reliably comparable to each other, there is no such correlation.

If the statements above are all true, which of the following can properly be inferred on the basis of them?
(A) Countries with large national budget deficits tend to restrict foreign trade.
(B) Reliable comparisons of the deficit figures of one country with those of another are impossible.
(C) Reducing a country’s national budget deficit will not necessarily result in a lowering of any trade deficit that country may have.
(D) When countries are ordered from largest to smallest in terms of population, the smallest countries generally have the smallest budget and trade deficits.
(E) Countries with the largest trade deficits never have similarly large national budget deficits.

6. Many breakfast cereals are fortified with vitamin supplements. Some of these cereals provide 100 percent of the recommended daily requirement of vitamins. Nevertheless, a well-balanced breakfast, including a variety of foods, is a better source of those vitamins than are such fortified breakfast cereals alone.

Which of the following, if true, would most strongly support the position above?
(A) In many foods, the natural combination of vitamins with other nutrients makes those vitamins more usable by the body than are vitamins added in vitamin supplements.
(B) People who regularly eat cereals fortified with vitamin supplements sometimes neglect to eat the foods in which the vitamins occur naturally.
(C)Foods often must be fortified with vitamin supplements because naturally occurring vitamins are removed during processing.
(D) Unprocessed cereals are naturally high in several of the vitamins that are usually added to fortified breakfast cereals.
(E) Cereals containing vitamin supplements are no harder to digest than similar cereals without added vitamins.

Explanation: By pointing out that, when occurring in natural combination with other nutrients, vitamins are more usable by the body than are those same vitamins when added as a supplement, choice A provides reason to believe that a well-balanced breakfast is a better source of vitamins than is a fortified breakfast cereal. A is the best answer.
Choice B does not support the position taken, although the position taken, if correct, is relevant to the people mentioned. Choice E describes a similarity between fortified cereals and other cereals. Choice C provides a reason for adding supplements to processed cereals, and choice D gives information about unprocessed cereals, but neither adds support for the alleged advantage of a well-balanced breakfast over a fortified cereal.

7. Which of the following best completes the passage below?
The more worried investors are about losing their money, the more they will demand a high potential return on their investment; great risks must be offset by the chance of great rewards. This principle is the fundamental one in determining interest rates, and it is illustrated by the fact that——.
(A) successful investors are distinguished by an ability to make very risky investments without worrying about their money
(B) lenders receive higher interest rates on unsecured loans than on loans backed by collateral
(C) in times of high inflation, the interest paid to depositors by banks can actually be below the rate of inflation
(D) at any one time, a commercial bank will have a single rate of interest that it will expect all of its individual borrowers to pay
(E) the potential return on investment in a new company is typically lower than the potential return on investment in a well-established company

Explanation: Since an unsecured loan is more risky, from the lender’s point of view, than a loan baked by collateral, the fact that lenders receive higher interest rates for unsecured loans is an illustration of the principle outlined in the passage. Thus, choice B is the best answer.
None of the other choices gives a clear instance in which increased risk is compensated by the potential for increased return. Choice A does not concern return on investment at all. Choice C is an instance of low return unrelated to risk. In choice D, contrary to the principle, the rate of return remains constant despite possible variations in risk, and choice E also runs counter to the principle if investments in well-established companies entail less risk.

8. Sales of telephones have increased dramatically over the last year. In order to take advantage of this increase, Mammoth Industries plans to expand production of its own model of telephone, while continuing its already very extensive advertising of this product.

Which of the following, if true, provides most support for the view that Mammoth Industries cannot increase its sales of telephones by adopting the plan outlined above?
(A) Although it sells all of the telephones that it produces, Mammoth Industries’ share of all telephone sales has declined over the last year.
(B) Mammoth Industries’ average inventory of telephones awaiting shipment to retailers has declined slightly over the last year.
(C) Advertising has made the brand name of Mammoth Industries’ telephones widely known, but few consumers know that Mammoth Industries owns this brand.
(D) Mammoth Industries’ telephone is one of three brands of telephone that have together accounted for the bulk of the last year’s increase in sales.
(E) Despite a slight decline in the retail price, sales of Mammoth Industries’ telephones have fallen in the last year.

Explanation: Choice E indicates that Mammoth’s telephones already fail to participate in the industry trend of higher sales despite heavy advertising. Producing more of the same model would thus be unlikely to generate increased sales for Mammoth, so E is the best answer.
If Mammoth has sold all the telephones it produced, it might increase sales by producing more, even if it has lost market share, as choice A states. Choice D indicates that Mammoth’s sales are increasing, and similarly for B if the decrease in inventory results from retailers taking delivery of more telephones. So long as consumers recognize the brand name of Mammoth’s telephones, as choice C states, it probably does not matter whether they associate it with Mammoth.

9. Many institutions of higher education suffer declining enrollments during periods of economic slowdown. At two-year community colleges, however, enrollment figures boom during these periods when many people have less money and there is more competition for jobs.

Each of the following, if true, helps to explain the enrollment increases in two-year community colleges described above EXCEPT:
(A) During periods of economic slowdown, two-year community colleges are more likely than four-year colleges to prepare their students for the jobs that are still available.
(B) During periods of economic prosperity, graduates of two-year community colleges often continue their studies at four-year colleges.
(C) Tuition at most two-year community colleges is a fraction of that at four-year colleges.
(D) Two-year community colleges devote more resources than do other colleges to attracting those students especially affected by economic slowdowns.
(E) Students at two-year community colleges, but not those at most four-year colleges, can control the cost of their studies by choosing the number of courses they take each term.

Explanation: Four of the choices give reasons why, in an economic showdown, many people would choose a two-year college. Choice A indicates that a two-year college education gives one a better chance of finding a job when economic conditions are poor. Choice C and E indicate why people with less money might prefer two-year colleges. Finally, choice D suggests that more is being done to attract people whose lives are affected by the slowdown to two-year than to four-year colleges.
Choice B, the best answer, might explain the decreased enrollment at four-year colleges during the slowdown, but because it deals with graduates of two-year colleges it cannot explain why enrollment at these colleges might increase.

10. In tests for pironoma, a serious disease, a false positive result indicates that people have pironoma when, in fact, they do not; a false negative result indicates that people do not have pironoma when, in fact, they do. To detect pironoma most accurately, physicians should use the laboratory test that has the lowest proportion of false positive results.

Which of the following, if true, gives the most support to the recommendation above?
(A) The accepted treatment for pironoma does not have damaging side effects.
(B) The laboratory test that has the lowest proportion of false positive results causes the same minor side effects as do the other laboratory tests used to detect pironoma.
(C) In treating pironoma patients, it is essential to begin treatment as early as possible, since even a week of delay can result in loss of life.
(D) The proportion of inconclusive test results is equal for all laboratory tests used to detect pironoma.
(E) All laboratory tests to detect pironoma have the same proportion of false negative results.

Explanation: The most accurate test for pironoma would be the one with the fewest false results. If all tests have the same proportion of false negatives, then the most accurate is the one that has the lowest proportion of false positives. Thus, E supports the recommendation and is the best answer.
Choice A and C deal with the treatment for pironoma and are irrelevant to the accuracy of tests pironoma. Choice B deals with the side effects of tests for pironoma, and does not address their accuracy. That the proportion of inconclusive test results is equal for all tests (choice D) leaves open the question of which test is more accurate, since it does not indicate which test has fewest false results.

11. When a polygraph test is judged inconclusive, this is no reflection on the examinee. Rather, such a judgment means that the test has failed to show whether the examinee was truthful or untruthful. Nevertheless, employers will sometimes refuse to hire a job applicant because of an inconclusive polygraph test result.
Which of the following conclusions can most properly be drawn from the information above?
Most examinees with inconclusive polygraph test results are in fact untruthful.
Polygraph tests should not be used by employers in the consideration of job applicants.
An inconclusive polygraph test result is sometimes unfairly held against the examinee.
A polygraph test indicating that an examinee is untruthful can sometimes be mistaken.
Some employers have refused to consider the results of polygraph tests when evaluating job applicants.

Explanation: The passage indicates that an inconclusive polygraph test tells nothing about the person who has taken the test, and yet employers sometimes refuse to hire someone whose results from such a test are inclusive. Treating lack of information as if it were unfavorable evidence about a person can reasonably be considered unfair. There, C is the best choice.
Choice A is not supported, since the passage says that an inconclusive polygraph test is no reflection on the examinee. Neither B nor D is supported, since the information given includes nothing either implicit or explicit about polygraph tests that yield conclusive results. Since the passage is consistent with both E and its denial, E is not supported.

12. According to the new office smoking regulations, only employees who have enclosed office may smoke at their desks. Virtually all employees with enclosed offices are at the professional level, and virtually all secretarial employees lack enclosed offices. Therefore, secretaries who smoke should be offered enclosed offices.
Which of the following is an assumption that enables the conclusion above to be properly drawn?
(A) Employees at the professional level who do not smoke should keep their enclosed offices.
(B) Employees with enclosed offices should not smoke at their desks, even though the new regulations permit them to do so.
(C) Employees at the secretarial level should be allowed to smoke at their desks, even if they do not have enclosed offices.
(D) The smoking regulations should allow all employees who smoke an equal opportunity to do so, regardless of an employee’s job level.
(E) The smoking regulations should provide equal protection from any hazards associated with smoking to all employees who do not smoke.

Explanation: The regulations allow some employees-those with enclosed offices-but not others the opportunity to smoke at their desks. If it is assumed that the regulations should allow all employees equal opportunity to smoke, those who are currently denied this opportunity should be given it, and so secretaries who smoke should be offered enclosed offices. Therefore, choice D is the best answer.
None of the other choices enables the conclusion to be properly drawn. Choice A tends to conflict with the conclusion, unless some enclosed offices are vacant. Choice B supports no conclusion about how secretaries should be treated, and choice C undermines the conclusion. Finally, nonsmokers already have equal protection from hazards, so choice E cannot be used to justify making any changes.

13. Dental researchers recently discovered that tooth-brushes can become contaminated wth bacterial that cause pneumonia and strep throat. They found that contamination usually occurs after toothbrushes have been used for four weeks. For that reason, people should replace their toothbrushes at least once a month.
Which of the following, if true, would most weaken the conclusion above?
(A) The dental researchers could not discover why toothbrush contamination usually occurred only after toothbrushes had been used for four weeks.
(B) The dental researchers failed to investigate contamination of toothbrushes by viruses, yeasts, and other pathogenic microorganisms.
(C) The dental researchers found that among people who used toothbrushes contaminated with bacterial that cause pneumonia and strep throat, the incidence of these diseases was no higher than among people who used uncontaminated toothbrushes.
(D) The dental researchers found that people who rinsed their toothbrushes thoroughly in hot water after each use were as likely to have contaminated toothbrushes as were people who only rinsed their toothbrushes hurriedly in cold water after each use.
(E) The dental researchers found that, after six weeks of use, greater length of use of a toothbrush did not correlate with a higher number of bacterial being present.

Explanation: According to choice C, using a contaminated toothbrush does not increase the incidence of infection, so the recommendation to replace a toothbrush before it becomes contaminated is greatly undermined. Choice C is therefore the best answer.
Since the recommendation is based on the discovery that bacterial contamination occurs after about four weeks, the researchers’ inability to discover why contamination takes that long to appear does not weaken the recommendation (choice A), nor does their failure to investigate other forms of contamination (choice B), nor does the discovery that contamination does not worsen after six weeks (choice E). According to choice D, even thorough washing cannot prevent contamination, so replacing the toothbrush appears more essential, rather than less so.

Questions 14-15 are based on the following.
To protect certain fledgling industries, the government of country Z banned imports of the types of products those industries were starting to make. As a direct result, the cost of those products to the buyers, several export-dependent industries in Z, went up, sharply limiting the ability of those industries to compete effectively in their export markets.

14. Which of the following can be most properly inferred from the passage about the products whose importation was banned?
(A) Those products had been cheaper to import than they were to make within country Z’s fledgling industries.
(B) Those products were ones that country Z was hoping to export in its turn, once the fledgling industries matured.
(C) Those products used to be imported from just those countries to which country Z’s exports went.
(D) Those products had become more and more expensive to import, which resulted in a foreign trade deficit just before the ban.
(E) Those products used to be imported in very small quantities, but they were essential to country Z’s economy.

Explanation: In Z, when the government banned imports of certain products the cost of those produces rose, so the products must have been cheaper to import than they were to make in Z. Therefore choice A is the best answer.
None of the other choices can be inferred. Country Z need have had no plan to export those products later (choice B), nor need the products have come previously from those countries to which country Z exported goods (choice C). The products need not have become more expensive before the ban (choice D), and they could have been imported in relatively large quantities (choice E).

15. Which of the following conclusions about country Z’s adversely affected export-dependent industries is best supported by the passage?
(A) Profit margins in those industries were not high enough to absorb the rise in costs mentioned above.
(B) Those industries had to contend with the fact that other countries banned imports from country Z.
(C) Those industries succeeded in expanding the domestic market for their products.
(D) Steps to offset rising materials costs by decreasing labor costs were taken in those industries.
(E) Those industries started to move into export markets that they had previously judged unprofitable.

Explanation: When the cost of the products rose, the competitive ability of those export-dependent industries that bought them was sharply limited. This fact strongly supports the claim that those industries did not have sufficiently high profit margins to enable them to absorb the price increase, so choice A is the best answer.
Given the limitation on their competitive ability, it is unlikely that those industries would be able either to expand their domestic markets (choice C) or to enter into new export markets (choice E). The other choices relate situations that would be possible but that are not strongly supported: other countries could have continued to permit imports from Z (choice B), and the industries may have unable to decrease labor costs (choice D).

16.The difficulty with the proposed high-speed train line is that a used plane can be bought for one-third the price of the train line, and the plane, which is just as fast, can fly anywhere. The train would be a fixed linear system, and we live in a world that is spreading out in all directions and in which consumers choose the free-wheel systems (cars, buses, aircraft), which do not have fixed routes. Thus a sufficient market for the train will not exist.
Which of the following, if true, most severely weakens the argument presented above?
(A) Cars, buses, and planes require the efforts of drivers and pilots to guide them, whereas the train will be guided mechanically.
(B) Cars and buses are not nearly as fast as the high-speed train will be.
(C) Planes are not a free-wheel system because they can fly only between airports, which are less convenient for consumers than the high-speed train’s stations would be.
(D) The high-speed train line cannot use currently underutilized train stations in large cities.
(E) For long trips, most people prefer to fly rather than to take ground-level transportation.

Explanation: The author argues that planes, since they are a free-wheel system, will be preferred to the high-speed train. Choice C weakens the argument by pointing out that planes are not a free-wheel system and are les convenient than the high-speed train would be. Thus C is the best answer.
The special feature of the high-speed train described in A is not one that clearly affects consumer choice one way or the other way. Since it is planes that would compete effectively with the proposed trains, the fact that cars and buses might not do so is irrelevant. Non-availability of certain station (choice D) and the consumer preferences described in choice E tend to make the proposed train less, not more, attractive and so both choices strengthen the argument.

17.Leaders of a miners’ union on strike against Coalco are contemplating additional measures to pressure the company to accept the union’s contract proposal. The union leaders are considering as their principal new tactic a consumer boycott against Gasco gas stations, which are owned by Energy Incorporated, the same corporation that owns Coalco.
Answer to which of the following questions is LEAST directly relevant to the union leaders’ consideration of whether attempting a boycott of Gasco will lead to acceptance of their contract proposal?
(A) Would revenue losses by Gasco seriously affect Energy Incorporated?
(B) Can current Gasco customers easily obtain gasoline elsewhere?
(C) Have other miners’ unions won contracts similar to the one proposed by this union?
(D) Have other unions that have employed a similar tactic achieved their goals with it?
(E) Do other corporations that own coal companies also own gas stations?

Explanation: Whether corporations, other than Energy Incorporated, that own coal companies also own gas stations is not directly relevant to whether attempting a boycott of Gasco gas stations will coerce Coalco to accept the contract proposal. Thus choice E is the best answer.
Each of the other four questions is relevant to evaluating the chances the union strategy has of succeeding. Choice A bears on whether the strategy would apply sufficient economic pressure on Energy Incorporated. Choice B is relevant to whether consumers can respond to the call for a boycott. Choice C is relevant to whether the union’s contract proposal is a reasonable one. Choice D is relevant because a successful precedent would favorably reflect on the union’s chances of success.

Questions 18-19 are based on the following.
Transnational cooperation among corporations is experiencing a model renaissance among United States firms, even though projects undertaken by two or more corporations under a collaborative agreement are less profitable than projects undertaken by a singly corporation . The advantage of transnational cooperation is that such joint international projects may allow United States firms to win foreign contracts that they would not otherwise be able to win.

18. Which of the following statements by a United States corporate officer best fits the situation of United States firms as described in the passage above?
(A) “We would rather make only a share of the profit and also risk only a share of a possible loss than run the full risk of a loss.”
(B) “We would rather make a share of a relatively modest profit than end up making none of a potentially much bigger profit.”
(C) “We would rather cooperate and build good will than poison the business climate by all-out competition.”
(D) “We would rather have foreign corporations join us in American projects than join them in projects in their home countries.”
(E) “We would rather win a contract with a truly competitive bid of our own than get involved in less profitable collaborative agreements.”

Explanation: According to the passage, for certain foreign contracts United States firms can either cooperate and hope to earn a modest profit, or not cooperate, not win the contract, and earn no part of a larger profit. This is how choice B describes the situation, so choice B is the best answer.
In order to earn a profit, United States firms must cooperate, so the alternatives described in several of the choices are not in practice open to them: the alternatives of a modest risk versus a full risk (choice A)., cooperation versus competition (choice C), and winning on their own versus collaborating (choice E). Since they do not have the same need to cooperate with foreign corporations to win American contracts, choice D does not fit either.

19. Which of the following is information provided by the passage above?
(A) Transnational cooperation involves projects too big for a single corporation to handle.
(B) Transnational cooperation results in a pooling of resources leading to high-quality performance.
(C) Transnational cooperation has in the past been both more common and less common than it is now among United States firms.
(D) Joint projects between United States and foreign corporation are not profitable enough to be worth undertaking.
(E) Joint projects between United States and foreign corporations benefit only those who commission the projects.

Explanation: To say that transnational cooperation is experiencing a modest renaissance means that it used to be relatively common, became less so, and is now becoming more common again. Therefore choice C is the best answer, since it follows from that statement.
None of the other choices presents information provided by the passage. The passage says nothing about the size of the projects (choice A), nor about the quality of work in cases of transnational cooperation (choice B). Since the passage strongly suggests transnational cooperation can be profitable for the firms concerned, it thereby tends to contradict both the claims that joint projects are not profitable (choice D) and that they only benefit those who commission the projects (choice E).

20. A compelling optical illusion called the illusion of velocity and size makes objects appear to be moving more slowly the larger the objects are. Therefore, a motorist’s estimate of the time available for crossing a highway with a small car approaching is bound to be lower than it would be with a large truck approaching.
The conclusion above would be more properly drawn if it were made clear that the
(A) truck’s speed is assumed to be lower than the car’s
(B) truck’s speed is assumed to be the same as the car’s
(C) truck’s speed is assumed to be higher than the car’s
(D) motorist’s estimate of time available is assumed to be more accurate with cars approaching than with trucks approaching
(E) motorist’s estimate of time available is assumed to be more accurate with trucks approaching than with cars approaching

Explanation: If the truck’s speed is assumed to be the same the car’s, then since the truck is larger, the optical illusion will make it appear that there is more time to cross the highway with the truck approaching than with the car approaching. Thus, choice B helps in establishing the conclusion and is the best answer.
If the truck’s speed is lower than the cars (choice A), the conclusion does not depend on the illusion. If the truck’s speed is higher than the car’s (choice C), the speed of the truck might counteract the illusion’s effect. Since the illusion works as stated regardless of what vehicle the estimate happens to be accurate for, neither choice D nor choice E assists in drawing the conclusions.

21. Biological functions of many plants and animals vary in cycles that are repeated every 24 hours. It is tempting to suppose that alteration in the intensity of incident light is the stimulus that controls these daily biological rhythms. But there is much evidence to contradict this hypothesis.
Which of the following, if known, is evidence that contradicts the hypothesis stated in lines 2-5 above?
(A) Human body temperature varies throughout the day, with the maximum occurring in the late afternoon and the minimum in the morning.
(B) While some animals, such as the robin, are more active during the day, others, such as mice, show greater activity at night.
(C) When people move from one time zone to another, their daily biological rhythms adjust in a matter of days to the periods of sunlight and darkness in the new zone.
(D) Certain single-cell plants display daily biological rhythms even when the part of the cell containing the nucleus is removed.
(E) Even when exposed to constant light intensity around the clock, some algae display rates of photosynthesis that are much greater during daylight hours than at night.

Explanation: Algae whose rate of photosynthesis varies on a 24-hour basis even when they are under constant light constitute evidence against the hypothesis that it is alterations in light that control biological cycles. Therefore choice E is the best answer.
Choices A and B describe biological cycles, but provide no evidence about what controls them. Choice C says that cycles can become adapted to new patterns of light, weakly supporting the hypothesis that alterations in light control cycles. Finally, choice D provides evidence against a different hypothesis, namely, that it is the cell nucleus of single-cell plants that controls their biological cycles.

22. Although migraine headaches are believed to be caused by food allergies, putting patients on diets that eliminate those foods to which the patients have been demonstrated to have allergic migraine reactions frequently does not stop headaches. Obviously, some other cause of migraine headaches besides food allergies much exist.
Which of the following, if true, would most weaken the conclusion above?
(A) Many common foods elicit an allergic response only after several days, making it very difficult to observe links between specific foods patients eat and headaches they develop.
(B) Food allergies affect many people who never develop the symptom of migraine headaches.
(C) Many patients report that the foods that cause them migraine headaches are among the foods that they most enjoy eating.
(D) Very few patients have allergic migraine reactions as children live migraine-free adult lives once they have eliminated from their diets foods to which they have been demonstrated to be allergic.
(E) Very rarely do food allergies cause patients to suffer a symptom more severe than that of migraine headaches.

Explanation: If it is difficult to determine which foods cause migraines, then some foods that cause allergic reactions might not have been demonstrated to do so. Hence, if choice A is true, eliminating foods that have been demonstrated to cause migraines might not eliminate migraines, even if food allergies are the only cause of migraines. Choice A is the best answer.
Neither the fact some food allergies do not result in migraines (choice B), nor the fact that few allergies result in symptoms more severe than migraines. Choice C suggests that migraine suffers do not naturally avoid the foods at issue. Choice D reiterates the information that eliminating certain foods does not usually solve the problem.

23. The technological conservatism of bicycle manufacturers is a reflection of the kinds of demand they are trying to meet. The only cyclists seriously interested in innovation and willing to pay for it are bicycle racers. Therefore, innovation in bicycle technology is limited by what authorities will accept as standard for purpose of competition in bicycle races.
Which of the following is an assumption made in drawing the conclusion above?
(A) The market for cheap, traditional bicycles cannot expand unless the market for high-performance competition bicycles expands.
(B) High-performance bicycles are likely to be improved more as a result of technological innovations developed in small workshops than as a result of technological innovations developed in major manufacturing concerns.
(C) Bicycle racers do not generate a strong demand for innovations that fall outside what is officially recognized as standard for purposes of competition.
(D) The technological conservatism of bicycle manufacturers results primarily from their desire to manufacture a product that can be sold without being altered to suit different national markets.
(E) The authorities who set standards for high-performance bicycle racing do not keep informed about innovative bicycle design.

Explanation: If racers, the only cyclists interested in innovation, created a strong demand for innovations for purposes other than official competition, then the conclusion would not follow. Therefore choice C-which asserts that racers generate no such demand-is assumed and is the best answer.
Since the argument is stated generally in terms of where demand for innovation lies and how manufacturers respond to demand, no assumption is made about the structure of the market for bicycles themselves (choice A) nor about which manufactures are most likely to produce innovations (choice B). Choice D presents another pressure toward technological conservatism, but the pressure is not required by the argument. Finally, the authorities may keep a close eye on innovation (choice E) without the argument being affected.

24. Spending on research and development by United States businesses for 1984 showed an increase of about 8 percent over the 1983 level. This increase actually continued a downward trend evident since 1981 – when outlays for research and development increased 16.4 percent over 1980 spending. Clearly, the 25 percent tax credit enacted by Congress in 1981, which was intended to promote spending on research and development, did little or nothing to stimulate such spending.
The conclusion of the argument above cannot be true unless which of the following is true?
(A) Business spending on research and development is usually directly proportional to business profits.
(B) Business spending for research and development in 1985 could not increase by more than 8.3%.
(C) Had the 1981 tax credit been set higher than 25%, business spending for research and development after 1981 would have increased more than it did.
(D) In the absence of the 25% tax credit, business spending for research and development after 1981 would not have been substantially lower than it was.
(E) Tax credits market for specific investments are rarely effective in inducing businesses to make those investments.

Explanation: The conclusion that the tax credit did nothing to stimulate spending on research and development would not be true if, without the credit, such spending would have been even lower than it actually was. Thus choice D must be true for the conclusion to be true and is the best answer.
Since a tax credit generally improves business profits, if the conclusion is true choice A is unlikely to be true. If the tax credit was ineffective, some other factors must determine the level of spending, and could lead to much higher levels of spending in 1985 (against choice B), and could render a higher level of tax credit ineffective (against choice C), but it could be that credits are generally effective (against choice E).

25. Treatment for hypertension forestalls certain medical expenses by preventing strokes and heart disease. Yet any money so saved amounts to only one-fourth of the expenditures required to treat the hypertensive population. Therefore, there is no economic justification for preventive treatment for hypertension.
Which of the following, if true, is most damaging to the conclusion above?
(A) The many fatal strokes and heart attacks resulting from untreated hypertension cause insignificant medical expenditures but large economic losses of other sorts.
(B) The cost, per patient, of preventive treatment for hypertension would remain constant even if such treatment were instituted on a large scale.
(C) In matters of health care, economic considerations should ideally not be dominant.
(D) Effective prevention presupposes early diagnosis, and programs to ensure early diagnosis are costly.
(E) The net savings in medical resources achieved by some preventive health measures are smaller than the net losses attributable to certain other measures of this kind.

Explanation: If the results of untreated hypertension cause large economic losses, as choice A claims, then the treatment of hypertension may well be economically justifiable. Therefore choice A is most damaging to the conclusion and is the best answer.
Choices B and D tend to support the conclusion; choice B says that making preventive treatment widespread would not introduce economies of scale, and choice D identifies one aspect of prevention that is both costly and essential. Choice C undermines a different conclusion-that society should not support treatment for hypertension-but does not damage the conclusion actually drawn. The fact that different preventive health measures have different economic consequences (choice D) gives no specific information about treatment for hypertension, and so cannot affect the conclusion drawn.

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