终于明白OG 11-89的答案了

自己觉得自己终于明白了！看到这道题也是经常被问的，所以share一下。也请NN们看看想得对不对。如下：

89. Networks of blood vessels in bats' wings serve only to disperse heat generated in flight. This heat is generated only because bats flap their wings. Thus paleontologists' recent discovery that the winged dinosaur Sandactylus had similar networks of blood vessels in the skin of its wings provides evidence for the hypothesis that Sandactylus flew by flapping its wings, not just by gliding.
The argument in the passage relies on which of the following assumptions?
(A) Sandactylus would not have had networks of blood vessels in the skin of its wings if these networks were of no use to Sandactylus.
(B) All creatures that fly by flapping their wings have networks of blood vessels in the skin of their wings.
(C) Winged dinosaurs that flapped their wings in flight would have been able to fly more effectively than winged dinosaurs that could only glide.
(D) If Sandactylus flew by flapping its wings, then paleontologists would certainly be able to find some evidence that it did so.
(E) Heat generated by Sandactylus in flapping its wings in flight could not have been dispersed by anything other than the blood vessels in its wings.

答案是A。

反反复复的对E迷惑过。我把网上的关于此题的帖子都看了，还是晕。后来我自己看啊看，忽然觉得E其实和B是一个意思——E说，拍翅膀的热量除了通过翅膀的血管外没有其它途径来散热。这应该是等于说，拍翅膀一定有血管。B和E都与原题的结论是反方向的，因此都不是assumption。
再从取非的角度来看——
E取非，是说S还有血管以外的途径来散发拍翅膀的热量。我们假设是鼻子吧。也就是取非为鼻子也能为拍翅膀散热。这对结论“有血管表明能拍翅膀”，好象没什么影响吧。不能削弱结论，也就不是答案。
A是说如果血管没用S就不长血管了，也就说S的血管是有用的。取非，血管没用。血管都没用了，怎么能有结论“有血管表明能拍翅膀”呢。这就是削弱了结论，所以A是正确的答案。

同意~

我还觉得E选项就是mindfree所谓的 out of scope，因为题目要求论证的是有血管-》拍翅膀。

但是E已经假设了恐龙可以拍翅膀，这就out of 逻辑链条的 scope 了

以下是引用qshiming在2009/8/17 3:27:00的发言：
在E上也挣扎了N久.... 现在好像明白了..... 假设不能以一个结论为前提, E好像就是错在这里了. 也不知道这样想是否正确

不正确