狒狒逻辑，高手请进？？？

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，我选了A。这题我现在知道了文章中的The more cholesterol we have in our blood, the higher the risk that we shall die of a heart attack.于A中的If a person has low blood cholesterol, then that person’s risk of fatal heart disease is low.意思不同。但是，如果A改为If a person has low blood cholesterol, then that person’s risk that s/he will die of a heart attack is low.，能否选A？？
另外，比如说“假期越长，学生越容易生病”和“假期越短，学生越不容易生病”
是否等价？前者是否支持后者，或者后者是否支持前者？？？

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.
答案是A，我选了E。为什么不能选E？？？

Questions 31-32
Political opinion and analysis outside the mainstream rarely are found on television talk shows, and it might be thought that this state of affairs is a product of the political agenda of the television stations themselves. In fact, television stations are driven by the same economic forces as sellers of more tangible goods. Because they must attempt to capture the largest possible share of the television audience for their shows, they air only those shows that will appeal to large numbers of people. As a result, political opinions and analyses aired on television talk shows are typically bland and innocuous.
31. An assumption made in the explanation offered by the author of the passage is that
(A) most television viewers cannot agree on which elements of a particular opinion or analysis are most disturbing.
(B) there are television viewers who might refuse to watch television talk shows that they knew would be controversial and disturbing.
(C) each television viewer holds some opinion that is outside the political mainstream, but those opinions are not the same for everyone.
(D) there are television shows on which economic forces have an even greater impact than they do on television talk shows.
(E) the television talk shows of different stations resemble one another in most respects.
32. The explanation offered by the author of the passage makes the assumption that
(A) television station executives usually lack a political agenda of their own
(B) bland and innocuous political opinions and analyses are generally in the mainstream
(C) political analysts outside the mainstream are relatively indifferent to the effect their analyses have on television viewers
(D) most television viewers are prepared to argue against allowing the expression of political opinions and analyses with which they disagree
(E) the political opinions of television station executives are not often reflected in the television shows their stations produce
这两题的问题好象没有什么不同，为什么答案不一样，是不是同一个论述可以同时拥有多个假设？？？

Questions 49-50
Joseph: My encyclopedia says that the mathematician Pierre de Fermat died in 1665 without leaving behind any written proof for a theorem that he claimed nonetheless to have proved. Probably this alleged theorem simply cannot be proved, since---as the article points out---no one else has been able to prove it. Therefore it is likely that Fermat was either lying or else mistaken when he made his claim.
Laura: Your encyclopedia is out of date. Recently someone has in fact proved Fermat’s theorem. And since the theorem is provable, your claim---that Fermat was lying or mistaken---clearly is wrong.
50. Which one of the following most accurately describes a reasoning error in Laura’s argument?
(A) It purports to establish its conclusion by making a claim that, if true, would actually contradict that conclusion.
(B) It mistakenly assumes that the quality of a person’s character can legitimately be taken to guarantee the accuracy of the claims that person has made.
(C) It mistakes something that is necessary for its conclusion to follow for something that ensures that the conclusion follows.
(D) It uses the term “provable” without defining it.
(E) It fails to distinguish between a true claim that has mistakenly between believed to be false and a false claim that has mistakenly been believed to be true.
答案是C，我理解C 的意思是倒因为果，但是怎么个倒因为果，没看出来。请教。