GWD-5-13

rouslinj

似乎跟其他帖子里提到的 5-13 不是同一个题：

Q13:
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 from feeding on infected whitefooted mice. However, certain other species on which the larvae feed do not harbor the bacterium. Therefore, if the population of these other species were increased, the number of ticks acquiring the bacterium―and hence the number of people contracting Lyme
disease—would likely decline.
Which of the following, if true, most strengthens the argument?
A. Ticks do not suffer any adverse consequences from carrying the bacterium that
causes Lyme disease in humans.
B. There are no known cases of a human’s contracting Lyme disease through contact
with white-footed mice.
C. A deer tick feeds only once while in the larval stage.
D. A single host animal can be the source of bacteria for many tick larvae.
E. None of the other species on which deer tick larvae feed harbor other bacteria that
ticks transmit to humans.

答案C。

我觉得 B 更好啊，因为它排除了人类被感染的其他原因。

而 C，跟题目提出的问题没有什么关系吧？

微笑的迪妮莎

同问

棕榈猫

fact1yme disease is caused by a bacterium transmitted to humans by deer ticks.

fact2:deer ticks pick up the bacterium while in the larval stage from feeding on infected whitefooted mice.

fact3:certain other species on which the larvae feed do not harbor the bacterium.

前提population of these other species were increased

结论1：the number of ticks acquiring the bacterium  结论2：the number of people contracting Lyme
disease—would likely decline.

fact1是结论1和结论2间的桥梁
要在前提和结论1之间架个桥：C＋fact2+fact3,即tick在幼虫期只进食一次，以其他品种为食，就不以infected whitefooted mice为食了，而除infected whitefooted mice之外其他品种都不携带该细菌，那么TICK感染到该细菌的机会就小了。

[此贴子已经被作者于2007-10-19 17:37:10编辑过]

棕榈猫

以下是引用rouslinj在2007-10-19 14:21:00的发言：

我觉得 B 更好啊，因为它排除了人类被感染的其他原因。

而 C，跟题目提出的问题没有什么关系吧？

你在选B时实际上默认了the number of ticks acquiring the bacterium减少的原因是infected whitefooted mice减少了，而文章只给出  population of these other species were increased，缺一个前提：TICK进食的总量不变。

只有进食总量不变，当吃other species的数量增多时，吃infected whitefooted mice的量才会减少

rouslinj

以下是引用棕榈猫在2007-10-19 17:35:00的发言：

...即tick在幼虫期只进食一次，以其他品种为食，就不以infected whitefooted mice为食了...

关键问题就在这里，“只吃一次”与“吃别的品种”之间存在什么联系？

难道不能“只吃一次”，但还是吃那个什么 mice 么？

棕榈猫

我认为，只吃一次，就减少了吃MICE的可能性。