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题库 / OG2016-CR-53
Humans get Lyme disease from infected ticks. Ticks get infected by feeding on animals with Lyme disease, but the ease of transmission from host animal to tick varies. With most species of host animal, transmission of Lyme disease to ticks is extremely rare, but white-footed mice are an exception, readily passing Lyme disease to ticks. And white-footed mouse populations greatly expand, becoming the main food source for ticks, in areas where biodiversity is in decline.
The information in the passage most strongly supports which of the following?
In areas where many humans are infected with Lyme disease, the proportion of ticks infected with Lyme disease is especially high.
Very few animals that live in areas where there are no white-footed mice are infected with Lyme disease.
Humans are less at risk of contracting Lyme disease in areas where biodiversity is high.
Ticks feed on white-footed mice only when other host species are not available to them.
The greater the biodiversity of an area, the more likely any given host animal in that area is to pass Lyme disease to ticks.
情景：人类从被感染的虱子上得莱姆病。虱子是因为有莱姆病的动物而被感染的，但是从动物身上传染给虱子的困难度是不同的。白脚老鼠很容易被传染莱姆病。白脚老鼠在生物多样化降低的地区正在扩张。
推理：由于推理文段中没有结论，所以本题为演绎推理。
选题方式：略
选项分析：
A选项：在那些很多人类感染莱姆病的地方，感染莱姆病的虱子的比率是非常高的。文段中只说过“人类从被感染的虱子上得莱姆病”，并没有提到这两者呈严格正比关系。
B选项：很少有住在没有白脚老鼠地方的动物被感染莱姆病。文段中只讲过白脚老鼠最容易传染病，并没有说过其它动物不能传染。
C选项： Correct. 在生物多样性高的地方，人类不容易感染莱姆病。因为白脚老鼠在生物多样性少的地方繁殖的好，所以人类在生物多样性多的地方自然会更不容易感染莱姆病。
D选项：只有在没有其它寄主的时候，虱子才会寄生在白脚老鼠身上。本选项讨论的是虱子的喜好，文段中没有提过。
E选项：生物多样性越多的地方，寄主越有可能把莱姆病传染给虱子。文段中没有提过本选项。
我觉得这道题有问题啊，生物多样性的下降，并不一定意味着生物多样性就少啊，一个是相对量，一个是绝对量。题目中说了With most species of host animal, transmission of Lyme disease to ticks is extremely rare, but white-footed mice are an exception，我觉得言下之意就是基本上没有其他途径可以传播疾病。所以B与C很难区分
我也是基于biodiversity is declining not equals biodiversity is low，选择才选择的B
B选项的tricky在于 主语是animal （感染） 而 题干里说的是human（感染）
同感，B的very few感觉对应了文段的rare
有道理
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