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20. A rise in the percentage of all 18-year-olds who were recruited by the armed services of a small republic between 1980 and 1986 correlates with a rise in the percentage of young people who dropped out of high school in that republic. Since 18-year-olds in the republic are generally either high school graduates or high school dropouts, the correlation leads to the conclusion that the republic’s recruitment rates for 18-year-olds depend substantially on recruitment rates for high school dropouts.

Which one of the following statements, if true, most weakens the argument?

A. A large number of 18-year-old high school graduates were recruited for the republic’s armed services in 1986 than in 1980.
B. Many of the high-technology systems used by the republic’s armed services can be operated only by individuals who have completed a high school education.
C. Between 1980 and 1986 the percentage of high school graduates among 18-year-olds recruited in the republic rose sharply.
D. Personnel of the republic’s armed services are strongly encouraged to finish their high school education.
E. The proportion of recruits who had completed at least two years of college education was greater in 1986 than in 1980.

参考答案：C
思路：题目的核心是要否定percentage of dropouts 与 percentage of recruitment的因果关系
A：典型的混淆相对数概念和绝对数概念，文中比较的是比率，选项给的是绝对数；
B：无关选项，和题目的核心比率没有太大关系。Tips: 注意many... only by.....这种表述。
C：正确，指出结论的错误属于false dilemma。
D：无关选项。此类错误属于false appeal。tips:注意.....（机构或人）strongly encourage something
E：无关选项，percentage of those completed college education和题目的核心比率没有太大关系。

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21. Historian: We can learn about the medical history of individuals through chemical analysis of their hair. It is likely, for example, that Isaac Newton’s psychological problems were due to mercury poisoning; traces of mercury were found in his hair. Analysis is now being done on a lock of Beethoven’s hair. Although no convincing argument has shown that Beethoven ever had a venereal disease, some people hypothesize that venereal disease caused his deafness. Since mercury was commonly ingested in Beethoven’s time to treat venereal disease, if researchers find a trace of mercury in his hair, we can conclude that this hypothesis is correct.

Which one of the following is an assumption on which the historian’s argument depends?

A. None of the mercury introduced into the body can be eliminated.
B. Some people in Beethoven’s time did not ingest mercury.
C. Mercury is an effective treatment for venereal disease.
D. Mercury poisoning can cause deafness in people with venereal disease.
E. Beethoven suffered from psychological problems of the same severity as Newton’s.

There should be 2 assumptions to support the hypothesis. The 1st assumption of the author is that only venereal disease will be treated by mercury in Beethoven’s time. The 2nd assumption is only some people in Beethoven's time will ingest mercury, if all people ingest mercury, the evidence is not useful. So, some people in Beethoven's time did not ingest mercury. The answer should be B.

A, E have nothing to do with the argument.
C is not necessary, 'Since mercury was commonly ingested in Beethoven’s time to treat venereal disease' is enough.
D is wrong: according to the author, it is the venereal disease that will cause the deafness, not the mercury poison.

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22. In 1992, a major newspaper circulated throughout North American paid its reporters an average salary paid by its principle competitors to their reporters. An executive of the newspaper argued that this practice was justified, since any shortfall that might exist in the reporters’ salaries is fully compensated by the valuable training they receive through their assignments.

Which one of the following, if true about the newspaper in 1992, most seriously undermines the justification offered by the executive?

A. Senior reporters at the newspaper earned as much as reporters of similar stature who worked for the newspaper’s principle competitors.
B. Most of the newspaper’s reporters had worked there for more than ten years.
C. The circulation of the newspaper had recently reached a plateau, after it had increased steadily throughout the 1980s.
D. The union that represented reporters at the newspaper was different from the union that represented reporters at the newspaper’s competitors.
E. The newspaper was widely read throughout continental Europe and Great Britain as well as North America.

参考答案：B
思路：否定low salaries is fully compensated by training
A：与结论无关
B：10年工作经验表示training的作用不大。
C：与结论无关。
D：与结论无关。
E：与结论无关。
评论：此题较难，只能用排除法作。正确选项也比较含糊，需要推理，这种题在gmat中出现的不多。

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23. On a certain day, nine scheduled flights on Swift Airlines were canceled. Ordinarily, a cancellation is due to mechanical problems with the airplane scheduled for a certain flight. However, since it is unlikely that Swift would have the mechanical problems with more than one or two scheduled flights on a single day, some of the nine cancellations were probably due to something else.
The argument depends on which one of the following assumptions?

A. More than one or two airplanes were scheduled for the nine canceled flights.
B. Swift Airlines has fewer mechanical problems than do other airlines of the same size.
C. Each of the canceled flights would have been longer than the average flight on Swift Airlines.
D. Swift Airlines had never before canceled more than one or two scheduled flights on a single day.
E. All of the airplanes scheduled for the canceled flights are based at the same airport.

参考答案：A 采用取非法。
思路：否定More than one or two airplanes were scheduled for the nine canceled flights.将削弱作者的结论。

A：取非削弱
B：无关。
C：无关。
D：无关。
E：无关。

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24. The interstitial nucleus, a sub-region of the brain’s hypothalamus, is typically smaller for male cats than for female cats. A neurobiologist performed autopsies on male cats who died from disease X, a disease affecting no more than .05 percent of male cats, and found that these male cats had interstitial nuclei that were as large as those generally found in female cats. Thus, the size of the interstitial nucleus determines whether or not male cats can contract disease X.

Which one of the following statements, if true, most seriously weakens the argument?

A. No female cats have been known to contract disease X, which is a subtype of disease Y.
B. Many male cats that contract disease X also contract disease Z, the cause of which is unknown.
C. the interstitial nuclei of female cats who contact disease X are larger than those of female cats who do not contract disease X.
D. Of 1,000 autopsies on male cats that did not contract disease X, 5 revealed interstitial nuclei larger than those of the average male cat.
E. The hypothalamus is known not to be causally linked to disease Y, and disease X is a subtype of disease Y.

E is the best answer. Disease X is the subtype is disease Y, if disease Y has no link with hypothalamus, X must have no link with hypothalamus.

A, C talked about the female cat, that can't weaken the argument.
B talked about another disease Z, doesn't weaken the argument.
D just shows some data, which cannot weaken the argument.

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25. There should be a greater use of gasohol. Gasohol is a mixture of alcohol and gasoline, and has a higher octane rating and fewer carbon monoxide emissions than straight gasoline. Burning gasohol adds no more carbon dioxide to the atmosphere than plants remove by photosynthesis.
Each of the following, if true, strengthens the argument above EXCEPT:

A. Cars run less well on gasoline than they do on gasohol.
B. Since less gasoline is needed with the use of gasohol, an energy shortage is less likely.
C. Cars burn on the average slightly more gasohol per kilometer than they do gasoline.
D. Gasohol is cheaper to produce and hence costs less at the pump than gasoline.
E. Burning gasoline adds more carbon dioxide to the atmosphere than plants can remove.

答案是C。解释：首先领会本argument的结论是：There should be a greater use of gasohol。根据提议，要选支持选项，即选出支持多使用gasohol的选项：
A: 用gasoline的汽车不如用gasohol的汽车好，起到支持作用
B: 说明使用gasohol能够降低发生能源短缺的可能性，当然起到支持作用
C: 汽车行驶一公里平均需要使用的gasohol比gasoline多，这说明了gasohol的一项劣势，不能起到支持作用
D: gasohol比gasoline具有较低的成本，支持。
E: 燃烧gasoline产生的二氧化碳比植物能消化的多，而argument中说gasohol产生的二氧化碳不比植物光合作用时能移除的多，所以优势显而易见。

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26. Barnes: The two newest employees at this company have salaries that are too high for the simple tasks normally assigned to new employees and duties that are too complex for inexperienced workers. Hence, the salaries and the complexity of the duties of these two newest employees should be reduced.

Which one of the following is an assumption on which Barnes’s argument depends?

A. The duties of the two newest employees are not less complex than any others in the company.
B. It is because of the complex duties assigned that the two newest employees are being paid more than is usually paid to newly hired employees.
C. The two newest employees are not experienced at their occupations.
D. Barnes was not hired at a higher-than-average starting salary.
E. The salaries of the two newest are no higher than the salaries that other companies pay for workers with a similar level of experience.

答案是C。解释:
A: 不是假设
B: 这似乎在为两个新雇员拿高工资找理由，所以不能支持结论。
C: 正确。因为原文中说对于不熟练的员工来说，工资太高了; 并且要降低工作的复杂程度。如果员工胜任的话，why bother? 所以，重要假设就是这些员工在岗位上不胜任。
D: 这个选项太离题了，而且似乎有贬低Barnes人格之嫌。
E: 这个起到了削弱结论的作用，所以不是assumption。

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27. These days, drug companies and health professionals alike are focusing their attention on cholesterol in the blood. The more cholesterol we have in our blood, the higher the risk that we shall die of a heart attack. The issue is pertinent since heart disease kills more North Americans every year than any other single cause. At least three factors---smoking, drinking, and exercise—can each influence levels of the cholesterol in the blood.

Which one of the following can be properly concluded from the passage?

A. If a person has low blood cholesterol, then that person’s risk of fatal heart disease is low.
B. Smoking in moderation can entail as great a risk of fatal heart disease as does heavy smoking.
C. A high-cholesterol diet is the principal cause of death in North America.
D. The only way that smoking increases one’s risk of fatal heart disease is by influencing the levels of cholesterol in the blood.
E. The risk of fatal heart disease can be altered by certain changes in lifestyle.

答案是E。解释：
A. 原文中说，胆固醇越高，生心脏病的可能性越大。A选项的内容是否命题，不一定成立。
B. 原文中没有提到此相关信息。
C. 显然不对，因为文中结尾明显说抽烟、饮酒和缺少运动也可以影响血液中胆固醇水平，所以不能保证C是正确的。
D. 文中没有说是only way哦。
E. 就是它了。可以通过调整抽烟、饮酒、运动等生活方式来减少心脏病的可能性。

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28. Ordinary mountain sickness, a common condition among mountain climbers, and one from which most people can recover, is caused by the characteristic shortage of oxygen in the atmosphere at high altitudes. Cerebral edema, a rarer disruption of blood circulation in the brain that quickly becomes life-threatening if not correctly treated from its onset, can also be caused by a shortage of oxygen. Since the symptoms of cerebral edema resemble those of ordinary mountain sickness, cerebral edema is especially dangerous at high altitudes.

Which one of the following is an assumption on which the argument depends?

(A) The treatment for ordinary mountain sickness differs from the treatment for cerebral edema.
(B) Cerebral edema can cause those who suffer from it to slip into a coma within a few hours.
(C) Unlike cerebral edema, ordinary mountain sickness involves no disruption of blood circulation in the brain.
(D) Shortage of oxygen at extremely high altitude is likely to affect thinking processes and cause errors of judgment.
(E) Most people who suffer from ordinary mountain sickness recover without any special treatment.

答案选A
这道题目先讲了ordinary mountain sickness怎么样的，然后又讲了cerebral edema是怎么样，它们两者有共同点就是symptoms of cerebral edema resemble those of ordinary mountain sicknes，所以如果不当心的话，就容易把cerebral edema 看成是ordinary mountain sickness那样的话is especially dangerous at high altitudes.
A. 选项，提出了一个假设，就是他们两者的医疗方法不同，因为如果相同的话，用治疗普通登山症的方法也可以治cerebral edema，就不会有危险了
B. 无关选项
C. 讲普通的登山症怎样，文中已经讲了，不是什么前提
D. 无关选项
E. 无关选项

The answer should be A,
the mountain climber know very well how to treat ordinary mountain sickness, since the symptoms are the alike, if they treat cerebral edema the same way as they treat ordinary mountain sickness, the danger of cerebral edema would be especially dangerous at high altitudes.

B,C :the description of B,C doesn't show any difference on high altitudes.
D : 'thinking processes and cause errors of judgment' were never mentioned in the description. It could be an answer, but the not so good as A.
E didn't answer why 'cerebral edema is especially dangerous at high altitudes'.

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29. The price of a full-fare coach ticket from Toronto to Dallas on Breezeway Airlines is the same today as it was a year ago, if inflation is taken into account by calculating prices in constant dollars. However, today 90 percent of the Toronto-to-Dallas coach tickets that Breezeway sells are discount tickets and only 10 percent are full-fare tickets, whereas a year ago half were discount tickets and half were full-fare tickets. Therefore, on average, people pay less today in constant dollars for a Breezeway Toronto-to-Dallas coach ticket than they did a year ago.

Which one of the following, if assumed, would allow the conclusion above to be properly drawn?

(A) A Toronto-to-Dallas full-fare coach ticket on Breezeway Airlines provides ticket-holders with a lower level of service today than such a ticket provided a year ago.
(B) A Toronto-to-Dallas discount coach ticket on Breezeway Airlines costs about the same in constant dollars as they did a year ago.
(C) All full-fare coach tickets on Breezeway Airlines cost the same in constant dollars as they did a year ago.
(D) The average number of coach passengers per flight that Breezeway Airlines carries from Toronto to Dallas today is higher than the average number per flight a year ago.
(E) The criteria that Breezeway Airlines uses for permitting passengers to buy discount coach tickets on the Toronto-to-Dallas route are different today than they were a year ago.

答案选B
本题所讲的，无非就是，people pay less today in constant dollars，而得出这个结论的证据是，以前10%有打折，现在一半有打折，那么，这个前提就是，他们的价格是一样的，不然，如果涨价，就不可能付的少了
A，service，无关
C，full-fare coach tickets cost the same 不等于打折后的也一样
D，无关
E，无关