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　　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.
　　本文提出一個(gè)現象：孤島上的大象變小了（標紅一句），并列出可能的解釋?zhuān)簺](méi)有天敵大體型沒(méi)有優(yōu)勢同時(shí)小體型耗能更低（標紅第二第三句），提出小型動(dòng)物恰好相反，在孤島上體型大更有利（標紅第四句）。
　　1. The primary purpose of the passage is toA. question the plausibility of one explanation sometimes offered for the dwarfing of certain species living on islandsB. argue that dwarfing of certain species living on islands occurred prior to the PleistoceneC. cite evidence suggesting that dwarfing may have adverse consequences for some species living on islandsD. present some possible explanations for the dwarfing of certain species living on islandsE. contrast the effects of insular conditions on species with large body size and species with small body

　　答案：D
　　解析：見(jiàn)上面概括
　　2. According to the passage, which of the following statements about body size in mammals is true?A. A large body is unfavorable to mammalian species’ survival under most conditions.B. A large body tends to benefit small mammals living on islands.
　　C. For most herbivorous mammals, a large body size is easier to sustain in the absence of large predators.D. Under most conditions, a small body is less beneficial to herbivorous mammals than to nonherbivorous mammals.
　　E. Among nonherbivorous mammals, a small body is more beneficial on an island than on a mainland.
　　答案：B
　　解析：標紅第四句，即全文后一句。