求助一道PREP上面的原题，感谢大家了

Cherliuiking

Every fall Croton's jays migrate south.  The jays always join flocks of migrating crookbeaks with which they share the same summer and winter territories.  If a jay becomes separated from the crookbeaks it is accompanying, it wanders until it comes across another flock of crookbeaks.  Clearly, therefore, Croton's jays lack the navigational ability to find their way south on their own.

Which of the following, if true, most strengthens the argument above?

A. Croton's jays lay their eggs in the nests of crookbeaks, which breed upon completing their southern migration.

B. The three species most closely related to crookbeaks do not migrate at all.

C. In the spring, Croton's jays migrate north in the company of Tattersall warblers.

D. Species other than Croton's jays occasionally accompany flocks of migrating crookbeaks.

E. In the spring, crookbeaks migrate north before Croton's jays do.
答案选A，为什么呢？

prayer

答案是C，不是A

prayer

mikrodj wrote:
Premise 1: Every fall Croton's jays migrate south.
Premise 2: The jays always join flocks of migrating crookbeaks with which they share the same summer and winter territories.
Premise 3: If a jay from the crookbeaks it is accompanying, it wanders until it comes across another flock of crookbeaks.
This implies that a jay needs a flock to migrate south.
Conclusion: Croton's jays lack the navigational ability to find their way south on their own.
Consider the following problem (perhaps not the best analogy)
David goes to the gym every Wednesday. Every time David goes to the gym, Richard goes with him. If Richard stops to buy something, David waits for him. Clearly, David lacks the navigational ability to find the way to his gym.
what would strengthen this argument?
Every time that David needs to go to the University, he calls Richard to find the way. If the author said that David can go on his own to the university this would hamper the conclusion that David lacks navigational ability.
Regarding the problem
(A) Croton's jays lay their eggs in the nests of crookbeaks which breed upon completing their southern migration.
does this account for the lack of navigability of the croton's jay?
Let me know if this helps. I know my explanation might be not really clear

来自manhattan的解释

Cherliuiking

谢谢，prayer nn

verssy

你们难道没有人觉得这题应该选E吗？

醒醒Shine

非常弱地问一句，这个crookbeak和C选项的Tattersall warblers一定是同一个东西吗？光做这题的时候，真的不知道啊！
大家做题的时候怎么合理推断的呢？

小皮麽西瓜

醒醒Shine 发表于 2014-3-31 14:26
非常弱地问一句，这个crookbeak和C选项的Tattersall warblers一定是同一个东西吗？光做这题的时候，真的不 ...

刚好在看寂静碰到这道题。。如果问strengthens就选C，因为C中说jays它再返回北方时还是要跟着别人才能回来，说明没方向感， warbler只是“别人”的一个例子，也可以换成其他的鸟；如果问weaken就选A， 因为去南方时跟着别的鸟，不是因为没方向感，而是有其他的因素，如要下蛋在别人窝里。。。。

醒醒Shine

小皮麽西瓜 发表于 2014-6-26 07:31
刚好在看寂静碰到这道题。。如果问strengthens就选C，因为C中说jays它再返回北方时还是要跟着别人才能回 ...

这个解释清晰多了，谢谢！

一只酵母君

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猪小王

小皮麽西瓜 发表于 2014-6-26 07:31
刚好在看寂静碰到这道题。。如果问strengthens就选C，因为C中说jays它再返回北方时还是要跟着别人才能回 ...

同意！