OG(11)-89

frozenrain

OG(11)-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)

想请教为什么(B)不是答案呢?

[此贴子已经被作者于2005-12-29 22:38:19编辑过]

seasnow

把A取非发现削弱S也靠翅膀飞的结论.

把B取非对结论没有影响, 因为B说反了: 应该是所有用翅膀飞的生物都有ne t wo r k s ..., 而不是所有有ne t wo r k s ...都用翅膀飞.

ri g h t ?

frozenrain

谢谢回答喔

可是 (B) 不就是: 用翅膀飞的生物都有 network吗?

All creatures
that fly by flapping their wings have networks of blood vessels in the skin of
their wings.

你的意思是说  (B) 不是个充分必要的条件：用飞的生物都有network；但是有network的生物不见得都飞，是这个意思吗？  

seasnow

so r r y , 我没说清楚, 冒号后面是B的错误.

不过你理解得很对, 就是B把充分和必要等同了. 所以取非之后起不到削弱作用.

"用飞的生物都有network；但是有network的生物不见得都飞", 就是这个意思, 一下点出了B的错误.

go o d !

乌龙茶

同意seasnow的解释。

把A中的not去掉，就变成Sandactylus would have had networks of blood vessels in the skin of
its wings if these networks were of no use to Sandactylus.削弱结论。加上not就是支持。

B选项犯了AA里面的错误，after sth and therefore because of sth。因果倒置了。