gwd17-34急求问

jason00

Q34:

During the month of May, crabs arrive on Delaware’s beaches to lay eggs.  Certain shorebirds depend on these eggs for food during their annual spring migration to their northern breeding grounds.  Delaware’s crab population has declined recently.  This decline, however, poses no serious threat to the migrating shorebird populations:  by remaining longer in Delaware, the birds will be able to eat enough crab eggs to allow them to complete their migration.

Which of the following, if true, most seriously weakens the argument?

1. No other food available to the birds on Delaware’s beaches is as nutritious and accessible as are crab eggs. 无关， 即使没有， 不能削弱靠延长时间来得到足够鸟蛋的可能性


2. The decline in the number of crabs on Delaware’s beaches is due to the harvesting of crabs by humans. 无关


3. There are more crabs on Delaware’s beaches than in any other area that the migrating birds pass through. 增强


4. The crabs do not conceal their eggs. 无关


5. The earlier in the season the shorebirds complete their migration, the more likely they are to breed successfully.

题干的推导关系为：蟹蛋量下降，但没有影响靠蛋哺育的鸟的数量，原因是鸟可以通过延长找蛋的时间来吃到足够多的蛋。E说越早来，哺育越成功。即晚来的可能失败，削弱题干推导关系。 削弱原推导所赖的依据