D为什么不对

deezy

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?

 

1. The numbers of the Baltimore oriole, a songbird that dose not eat budworms but is as dependent on South American coffee plantations as is the Tennessee warbler, are declining.
2. The spruce-budworm population has dropped because of a disease that can infect budworms but not Tennessee warblers.
3. The drop in the population of the spruce budworm is expected to be only temporary.
4. Many Tennessee warbler have begun migrating in the fall to places other than traditional coffee plantations.
5. Although many North American songbirds have declined in numbers, no other species has experienced as great a decline as has the Tennessee warbler.

答案是A，D为什么不对