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?
Croton's jays lay their eggs in the nests of crookbeaks, which breed upon completing their southern migration.
The three species most closely related to crookbeaks do not migrate at all.
In the spring, Croton's jays migrate north in the company of Tattersall warblers.
Species other than Croton's jays occasionally accompany flocks of migrating crookbeaks.
In the spring, crookbeaks migrate north before Croton's jays do.
情景:Croton's jays是一种需要迁徙的鸟。这种鸟的迁徙通常是和另外一种鸟同时发生的,如果一只Croton's jays掉队了,那么它就会等下一波鸟来了之后再走。因此,我们认为Croton's jays这种鸟是没有方向感的。
推理:
前提:如果一只Croton's jays掉队了,那么它就会等下一波鸟来了之后再走
结论:Croton's jays这种鸟是没有方向感的
答案预估:
其它能解释为何“如果一只Croton's jays掉队了,那么它就会等下一波鸟来了之后再走”的原因不存在。
或者,“Croton's jays这种鸟没有方向感”的其它必要条件(常理上能保真推理出的一切结果)。
选项分析:
A选项:Croton's jays会在Crookbeak的鸟巢中下蛋,Crookbeak会在向南迁徙的过程中孵化这些蛋。本选项可以解释为什么Croton's jays会跟着Crookbeak前行,即,是因为要向Crookbeak这种鸟的巢里下蛋,所以才会选择跟着Crookbeak迁徙,可以削弱推理文段。
B选项:和Crookbeak最相近的三个种类的鸟从来不迁徙。种类相近不代表行为和能力相同。
C选项:Correct. 在春季,Croton's jays会随着塔特萨尔莺的队伍向北迁徙。本选项是“Croton'sjays这种鸟没有方向感”的其它必要条件,即,如果真的没有方向感,那么无论什么时间,这种鸟都需要跟着别人飞。
D选项:除掉Croton's jays,其他种类的鸟很少和Crookbeak一起成群迁徙。其它鸟和Cookbeak以及Croton's jays没有关系。
E选项:在春天,Crookbeak会先于Croton's jays向北迁徙。向北迁徙时,Croton's jays不见得非要跟着Crookbeak飞,也许自己飞,也许跟着别的鸟飞。因此,本选项无法完成答案预估中给出的两种可能。
A. 他因削弱
BD. 其他鸟怎么样,与crookbeak迁移的真正原因无关
E. 削弱
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