Our study revealed that nest-guarding long-tailed skinks (a species of lizard) homed (returned to their nests) more successfully

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问题     Our study revealed that nest-guarding long-tailed skinks (a species of lizard) homed (returned to their nests) more successfully when displaced shorter distances. There are two reasons why homing success rates decreased with increasing displacement distance. One possibility is that females were simply displaced too far to find their way home. However, this is unlikely given that some individuals managed to find their way home from each distance we used. The second possibility deals with trade-offs between the risks associated with making a long return trip and the benefits of returning. Animals should expend energy only when the associated costs are low. As reptiles increase the time spent moving, their daily energy expenditure increases dramatically. The energetic costs of returning home and the chances that the eggs will have been preyed upon during the return trip both increase substantially as displacement distance increases. For example, the 130 hours (5.5 days) that female skinks spent returning from a distance of 300 meters is sufficient for an egg-eating snake to locate and prey upon the entire clutch. However, females with larger clutches were more likely to home at distances over 50 meters. For these females, the relative fitness benefits associated with having more eggs successfully hatch may outweigh the energetic costs of returning to a nest site, even if the nest may have already been preyed upon.
The claim in the highlighted sentence assumes which of the following about the individuals that managed to find their way home from each distance?

选项 A、They were less able to detect egg-eating predators than were the other long-tailed skinks studied.
B、They were more averse to risk than were the other long-tailed skinks studied
C、They expended less energy when homing than did the other long-tailed skinks studied.
D、They did not possess better homing skills than did the other long-tailed skinks studied.
E、They had significantly smaller clutches than did the other long-tailed skinks studied.

答案D

解析 本题相当于假设题,因此选择取反之后推翻原文的选项。选项D取反后的含义是这些蜥蜴具备更好的回家技能。这么一来,这个实验便有了两个变量:回家技能和回家距离。但是合理的实验应该只有一个变量,选项取反后增加一个变量,也就意味着这个实验不可靠,进而其对应的结论被推翻。选项符合取反后推翻原文的原则,故D正确。当然,这道题的简单做法便是其余选项均含有原因二才提及的信息,均为定位错误,只有选项D正确。
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本试题收录于: GRE VERBAL题库GRE分类
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