The answer, in one word, is aggression. Chipmunk species actively defend their ecological zones from encroachment by neighboring

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问题     The answer, in one word, is aggression. Chipmunk species actively defend their ecological zones from encroachment by neighboring species. The yellow pine chipmunk is more aggressive than the sagebrush chipmunk, possibly because it is a bit larger. It successfully bullies its smaller evolutionary cousin, excluding it from the pine forests. Experiments have shown that the sagebrush chipmunk is physiologically able to live anywhere in the Sierra Nevada, from high alpine zones to the desert. The little creature is apparently restricted to the desert not because it is specialized to live only there but because that is the only habitat where none of the other chipmunk species can live. The fact that sagebrush chipmunks tolerate very warm temperatures makes them, and only them, able to live where they do. The sagebrush chipmunk essentially occupies its habitat by default. In one study, ecologists established that yellow pine chipmunks actively exclude sagebrush chipmunks from pine forests; the ecologists simply trapped all the yellow pine chipmunks in a section of forest and moved them out. Sagebrush chipmunks immediately moved in, but yellow pine chipmunks did not enter sagebrush desert when sagebrush chipmunks were removed.
Paragraph 5 mentions all of the following as true of the relationship of sagebrush chipmunks to their habitats EXCEPT:

选项 A、Sagebrush chipmunks are able to survive in any habitat of the Sierra Nevada.
B、Sagebrush chipmunks occupy their habitat because of the absence of competition from other chipmunks.
C、Sagebrush chipmunks are better able to survive in hot temperatures than other species of chipmunks.
D、Sagebrush chipmunks spend the warm season at the higher elevations of the alpine zone.

答案D

解析
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