费费逻辑50, 133(原来的讨论还是想不明白）

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Laura: Your encyclopedia is out of date.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.
                    

请问C选项的意思，It mistakes something that is necessary for its conclusion to follow for something that ensures that the conclusion follows，完全看不懂句子，我觉得非常绕~要绕死了。。。

Questions 132-133

Nature constantly adjusts the atmospheric carbon level. An increase in the level causes the atmosphere to hold more heat, which causes more water to evaporate from the oceans, which causes increased rain. Rain washes some carbon from the air into the oceans, where it eventually becomes part of the seabed. A decrease in atmosphere carbon causes decreased evaporation from the oceans, which cause less rain, and thus less carbon is washed into the oceans. Yet some environmentalists worry that burning fossil fuels may raise atmospheric carbon to a dangerous level. It is true that a sustained increase would threaten human life. But the environmentalists should relax---nature will continually adjust the carbon level.

133. Which one of the following, if true, would most weaken the argument in the passage?

B.        It is not clear that breathing excess carbon in the atmosphere will have a negative effect on human life.

C.        Carbon is part of the chemical “blanket” that keeps the Earth warm enough to sustain human life.

D.       Breathing by animals releases almost 30 times as much carbon as does the burning of fossil fuels.

E.        The natural adjustment process, which occurs over millions of years, allow wide fluctuations in the carbon level in the short term.

这个我选D，我觉得E并没有weaken吧，E不就是说明nature adjust the carbon level么？