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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.
Which of the following elements in the debate over the origin of Varanus is NOT provided in the passage?
选项 A、The evidence that led Mertens to argue that Varanus originated in the Indo-Australian archipelago
B、The evidence that led early researchers to argue that Varanus originated in Australia
C、A possible explanation of how Varanus might have spread to the Indo-Australian archipelago if it had originated in Australia
D、A possible explanation of how Varanus might have spread to Australia if it had originated in the Indo-Australian archipelago
E、An indication of the general present-day distribution of Varanus species between Australia and the Indo-Australian archipelago
答案A
解析 Choice A is correct. The passage provides support for Mertens’ argument by providing later chromosomal evidence as well as geologic evidence but it does not provide nor describe the evidence with which Mertens originally argued. Choices B and E are incorrect because the passage states that early researchers argued for a specific origin for Varanus "because most existing species live in Australia," which indicates the present-day distribution of species. Choices C and D are incorrect because the passage provides geologic evidence to suggest a possible explanation for how Varanus may have spread to either Australia or the archipelago regardless of its origin.
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