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  3. Experts have differed about where the genus Varanus(monitor lizards)originated. Because most existing species live in Australia,

Experts have differed about where the genus Varanus(monitor lizards)originated. Because most existing species live in Australia,

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问题 Experts have differed about where the genus Varanus(monitor lizards)originated. Because most existing species live in Australia, early researchers concluded that Varanus originated in Australia and subsequently island hopped westward along the Indo-Australian archipelago. Herpetologist Robert Mertens later argued that Varanus probably originated in the archipelago. Chromosomal analysis has since supported Mertens’ contention, and in addition, geologic evidence points to a collision between the archipelago and the Australian landmass after Varanus evolved—a fact that could account for the genus’ present distribution.
A related puzzle for scientists is the present distribution of Varanus largest surviving species, the Komodo dragon. These carnivores live only on four small islands in the archipelago where, scientists note, the prey base is too small to support mammalian carnivores. But the Komodo dragon has recently been shown to manage body temperature much more efficiently than do mammalian carnivores, enabling it to survive on about a tenth of the food energy required by a mammalian carnivore of comparable size.
It can be inferred from the passage that the geographical distribution of the Komodo dragon is
选项 A、currently less restricted than it was at the time researchers first began investigating the origins of the genus Varanus
B、currently more restricted than it was at the time researchers first began investigating the origins of the genus Varanus
C、less restricted than is the distribution of the genus Varanus as a whole
D、more restricted than is the distribution of the genus Varanus as a whole
E、viewed as evidence in favor of the hypothesis that the genus Varanus originated in the Indo-Australian archipelago
答案D
解析 Choice D is correct. Because the Komodo dragon, a species of Varanus, is restricted to "four small islands in the archipelago" but "most existing species" of the genus Varanus as a whole live in Australia, the geographical distribution of the genus includes species in both places. The distribution of the Komodo dragon is restricted to only one of these places and is thus more restricted than the genus as a whole, not less restricted. Thus, Choice C is incorrect. Choices A and B are incorrect because the passage does not describe the specific change in the geographic distribution of the Komodo dragon, but rather just describes its present distribution. Choice E is incorrect because the passage does not present its discussion of the Komodo dragon as evidence for either hypothesis of the origin of Varanus but rather as a "related puzzle."
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