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标题: 问一道prep上逻辑 [打印本页]

作者: bony 时间: 2009-10-8 17:43
标题: 问一道prep上逻辑

Lyme disease is caused by a bacterium tansmitted to humans by deer ticks. Generally, deer ticks pick up the bacterium while in the larval stage by feed on infected white-footed mice. However, certain other species on which the larvae feed do not harbor the bacterium. If the population of these other species were increased, more of the larvae would be feeding on uninfected host, so the number of ticks acquiring the bacterium would decline.

问evaluate

A Whether populations of the other species on which deer tick larvae feed are found only in areas also inhabited by white-footed mice

B Whether the size of the deer tick population is currently limited by the availability of animals for the tick's laral stage to feed on

C Whether the infected deer tick population could be controlled by increasing the number of animals that prey on white-footed mice

D Whether deer ticks that were not infected as larvae can become infected as adults by feeding on deer on which infected deer ticks have fed

E Whether the other species on which deer tick larvae fed harbor any other bacteria that ticks transmit to humans

选B，请大侠指点，最好每个选项都解释一下，嘿嘿，先谢过！

作者: renxian 时间: 2009-10-8 20:00
请问evaluate什么呀？不清楚

作者: bony 时间: 2009-10-9 08:32

问下列哪个问题能知道了的话，就能evaluate幼虫感染细菌的数量会减少。。。。

有人知道么，快考了，急啊。。。。

作者: genius_fang 时间: 2009-10-9 09:24
题目的意思说人类感染L这种疾病是由于deer tick传播一种细菌。而这种细菌是由于deer tick在幼虫阶段寄生在一种受感染的老鼠身上而携带了这种细菌。而有一些其他的物种deer tick也会在其寄生，但却不会携带这种细菌。结论，如果其他这些物种增加了，那么更多的deer tick会寄生在没受感染的寄主上，于是人类感染这种疾病的数量也会减少。B选项说：deer tick的数量是否受当前可寄生的动物的数量所限制。如果回答yes，那么加强了原题，因为deer tick有限，寄生在infected host上的数量，那么寄生在必然减少，于是人类得病有减少。若回答是no，即使uninfected host增加，deer tick也大肆增加的话，寄生在infected host上的数量未必会减少，削弱的结论~~所以是评价了题目~~~选B。

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