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  3. During the Pleistocene epoch, several species of elephants isolated on islan

During the Pleistocene epoch, several species of elephants isolated on islan

游客2024-01-10  59
问题     During the Pleistocene epoch, several species of elephants isolated on islands underwent rapid dwarfing. This phenomenon was not necessarily confined to the Pleistocene, but may have occurred much earlier in the Southeastern Asian islands, although evidence is fragmentary. Several explanations are possible for this dwarfing. For example, islands often have not been colonized by large predators or are too small to hold viable predator populations. Once free from predation pressure, large body size is of little advantage to herbivores. Additionally, island habitats have limited food resources, a smaller body size and a need for fewer resources would thus be favored. Interestingly, the island rule is reversed for small mammals such as rodents, for which gigantism is favored under insular conditions. [br] The primary purpose of the passage is to
选项 A、question the plausibility of one explanation sometimes offered for the dwarfing of certain species living on islands
B、argue that dwarfing of certain species living on islands occurred prior to the Pleistocene
C、cite evidence suggesting that dwarfing may have adverse consequences for some species living on islands
D、present some possible explanations for the dwarfing of certain species living on islands
E、contrast the effects of insular conditions on species with large body size and species with small body
答案 D
解析 最后一句提到小动物会变大的目的是进一步论证岛屿对动物体型的影响，因此文章的主要目的就是在解释为什么大象会变小，所以选项D正确而选项E错误。A项错在question。B项属于细节。C项some species既可能指代大动物，也可能指代小动物，无论怎样都不对。
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