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.
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.
思路：否定low salaries is fully compensated by training
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.
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。
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.
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：