Guillemots are birds of Arctic regions.They feed on fish that gather beneath thin sheets of floating ice, and they nest on nearby land. Guillemots need 80 consecutive snow-free days in a year to raise their chicks, so until average temperatures in the Arctic began to rise recently, the guillemots' range was limited to the southernmost Arctic coast. Therefore, if the warming continues, the guillemots' range will probably be enlarged by being extended northward along the coast.

which of the following, if true, most seriously weaken the argument?

B   If the Arctic warming continues, guillemots' current predators are likely to succeed in extending their own range farther north.

D   If the Arctic warming continues, much of the thin ice in the southern Arctic will disppear.

这道题OG 上给出的答案是D。OG的解释也很明确，是因为并非扩大领域，而是替代了南部的领域。

可是我不理解的是B为什么不对呢？B成立的话说明捕食G这种鸟类的动物也向北扩展，那么G为了躲避捕食者，不就不能扩大向北的领域了吗？

请NN们指教！

无论Guillemots在南边还是往北扩展，predator应该都是存在的，因此应该不能削

弱吧。也不知道我说清楚没

呵呵。因为很多人没有做过diagnostic test.其实上面的题目相当难。

这个题的思路相当诡异。我印象中是这样。

因为在南面的时候Guillemots和predator是同时存在的。所以predator移到北方，guillemots也是会过去。注意：并不是MM 你的思路，predator过去了，guillemots就不过去了。所以这个按照ets的逻辑，guillemots的领地还是会扩大。所以B不对。

楼上有没有看og的解释。og说鸟儿往北跑了，但是原来的领地被融化掉了。

假设原来领地是a,现在往北扩大了b，但是原来的a里面融化掉了b =》 a+b-b=a. 面积不变。