2. 外语
  3. Historically, more cold-adapted antelope species originating in Eurasia have migrated into Africa, where the climate is generall

Historically, more cold-adapted antelope species originating in Eurasia have migrated into Africa, where the climate is generall

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问题     Historically, more cold-adapted antelope species originating in Eurasia have migrated into Africa, where the climate is generally warmer, than have warm-adapted African species into Eurasia. A likely explanation for this involves the fact that intercontinental migrations require both a land bridge connecting the two continents and the suitable habitat both on and across that land bridge. During periods of climatic cooling, such as the various ice ages, the land bridge is open for a long time (because sea level remains low) and is usable by cold-adapt species because cool habitats then extend across it. Thus during cooling most migrants would be expected to travel toward Africa, which is near the equator, since this is the direction dictated by habitat changes on a cooling Earth. In contrast, when the Earth is warm, the land bridge is reduced or gone because sea level is relatively high then. Only during the short lag between onset of global temperature change and sea level response can warm-adapted species migrate from the equator toward higher latitudes.
The author of the passage implies that during the “short lag”, a land bridge between Africa and Eurasia would
选项 A、be inhabited primarily by species of antelope originating in Eurasia
B、be characterized by areas of widely varying elevation above sea level
C、be inhabited by a wide diversity of antelope species
D、contain habitats that could sustain warm-adapt antelope species
E、contain habitats similar to habitats at much higher latitudes in Eurasia
答案D
解析 根据文章，在short lag期间，适应于温暖气候的羚羊可以迁徙到欧亚大陆，这意味着这个时期的大陆桥包含有适合这种物种的栖息地。A项应该是被起源于非洲的物种居住。
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