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

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 "second possibility" implies which of the following as a possible explanation for the female long-tailed skinks that failed to home from distances over 50 meters ?
选项 A、They had relatively small clutches.
B、They were unable to find their way home.
C、They lacked sufficient energy to home successfully.
D、They had male long-tailed skinks guarding their clutches.
E、They detected evidence of egg-eating snakes in the vicinity of their nests.
答案A
解析 根据原因二的思想，蜥蜴回家与否取决于回家之后能被成功孵化的蛋的数量与回家所消耗的能量之间的权衡。根据第十句，离家50米的蜥蜴，当巢穴很大的时候就会回家。那么离家50米但是不回家的蜥蜴，其原因就是巢穴小，因此选项A正确。B项这是原因一。与原因二无关，属于定位错误。C项这是一个陷阱选项。要注意“耗能高”和“自身没有足够能量”之间的关系。原文蜥蜴不回家是因为觉得回家“耗能高”，相比于能被孵化出来的蛋来说很不划算。原文没说蜥蜴本身有没有足够的能量。D项没提雄性。E项根据最后一句，即使有可能蛋都被吃了，只要离家近，或者巢穴足够大，蜥蜴还是愿意回家的，所以发现周围有蛇的证据不构成蜥蜴不回家的原因。
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