一条新思路:完全可以把题目理解为- A棉花和B棉花,A遭破坏,是虫太多导致的。对此加强-B也遭破坏;对此削弱-B没破坏。所以判断依据为B是否遭破坏。 这题完全和GWD-3-Q38异曲同工:-warbler鸣鸟数量下降,是因为咖啡田少了还是它吃的虫子少了。正确A项中Bo鸟不吃虫但数量也下降了。 可按是否吃虫把鸟分成A鸟(warbler)和B鸟(Bo)。 Kate: The recent decline in numbers of the Tennessee warbler, a North American songbird that migrates each fall to coffee plantations in South America, is due to the elimination of the dense tree cover that formerly was a feature of most South American coffee plantations.
Scott: The population of the spruce budworm, the warbler’s favorite prey in North America, has been dropping. This is a more likely explanation of the warbler’s decline.
Which of the following, if true, most seriously calls Scott’s hypothesis into question?
- The numbers of the Baltimore oriole, a songbird that does not eat budworms but is as dependent on South American coffee plantations as is the Tennessee warbler, are declining.
- The spruce-budworm population has dropped because of a disease that can infect budworms but not Tennessee warblers.
- The drop in the population of the spruce budworm is expected to be only temporary.
- Many Tennessee warbler have begun migrating in the fall to places other than traditional coffee plantations.
Although many North American songbirds have declined in numbers, no other species has experienced as great a decline as has the Tennessee warbler. 其实棉花是否有抗体只是将棉花分类而已! |