对选项理解 FEIFEI一题

wynyy2000

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Laura: Your encyclopedia is out of date.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. （句意理解！！）
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. 句意理解！！
L's line of reasoning is: someone has proved the theorem, so F is not lying or makes any mistake in his claim. 其他人证明了这个theorem,不代表f 也证明了 或者他的claim 就没问题，但对C，E选项的理解，我还是觉得绕，特别是E，大家帮帮！！

sdcar2010

Laura's premise is that the theory is provable. The fact that the theory is provable is necessary for the conclusion that Fermat has indeed proved the theory before his death. But this fact alone does not conclusively prove or sufficiently points out that Fermat has proved it. In other words, this fact alone is not a sufficient condition for the conclusion that Fermat has indeed proved the theory.

C points out this error in Laura's argument.

anjjule

谢谢sdcar2010,刚做到这题,你解释的很到位