新prep2-100，原T-9-Q28变体，请指教~

100.
            (30745-!-item-!-188;#058&005748)     (T-9-Q28. ��ɽ-7-13 , different type)

Lyme disease is caused by a bacterium transmitted to humans by deer ticks.  Generally, deer ticks pick up the bacterium while in the larval stage by feeding 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 hosts, so the number of ticks acquiring the bacterium would likely decline.

Which of the following would it be most important to ascertain in evaluating the argument?

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 larval 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 feed harbor any other bacteria that ticks transmit to humans

 正确答案是B

B的意思是不是，deer tick population的数量现在已经被它们可以feed on的animal的数量所限制了，言下之意就是the population of these other species were increased不成立，所以B回答yes的话就是削弱了？

请指教下

第一句话是对的，但是我觉的lz的言下之意稍微有点偏。

题干中的假设是tick的总数目不会变，因此更多的其他动物将会分流呆在white-footed mice上的tick的数量，从而导致带病菌的tick的数目降低。

这里的关键是判断这个假设会不会成立，如果B的回答是确定的话，那么只会繁殖出更多tick生活到新增的其他动物身上去，而在现有的white-footed mice身上的tick数目不会变，从而导致削弱论点so the number of ticks acquiring the bacterium would likely decline。

想问一下为什么D不对，是因为说feed on deer是题目中没提到的么？，所以D是无关？

因为D没有涉及到other species

所以对它回答YES OR NO，对于feed on the white-footed mice 和feed on other species的影响是一样的，没有对feed on other species能降低受细菌感染这个结论起到支持或削弱作用。

唉，还是很迷惑

同意

B的意思是：tick的数量是否受到幼虫阶段吃得动物来源的影响或者限制

YES-如果tick数量受到幼虫时期可吃到的食物的影响：可吃到的食物越多，tick的数量就越多，可能会分散在有细菌和没细菌的宿主身上，在白足鼠身上的tick不一定会decline-削弱

NO-如果tick数量不受幼虫时期可吃到的食物的影响：可吃到的食物再多，tick的数量也不变，那么就像题目中提到的，“if the population of these other species were increased,more of the larvae would be feeding on uninfected hosts, so the number of ticks acquiring the bacterium would likely decline”也就是说，有更多的tick转移阵地到没有细菌的宿主身上了，那么白足鼠身上的tick就减少了-加强

想问一下E为什么不对?

E: 如果the other species harbor any other bacteria , 那么deer tick 吃了以后,也会导致带病毒的deer tick 增加啊?