进来讨论一下，这题有好几个版本，我的版本目前还没有被讨论过

rachelxfr

Lyme disease is sometimes 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 white-footed 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.Many deer 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 direct contact with white-footed mice.

C.Any species the larvae feed on have enormous probabilities of transmitting Lyme disease to humans by deer ticks.

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.
这题该选什么？

peter3008

我认为是D
题目已经出很多变了。
a:无关选项。
b: 他因，削弱
C：削弱
D：加强，在假设总的tick数量不变的情况下，其实题目一直隐含这个假设
E: 起初没有看懂，特别绕，简化下，没有别的DT以食物的生物带有可以传染给人类的别的bacteria.提干的结论是the number of ticks acquiring the bacterium―and hence the number of people contracting Lyme disease—would likely decline,围绕的是lyme disease的bacterium，跟other B么有什么关系。

不知道对不对，请给出正确答案

胖胖胖胖

我认为是D
题目已经出很多变了。
a:无关选项。
b: 他因，削弱
C：削弱
D：加强，在假设总的tick数量不变的情况下，其实题目一直隐含这个假设
E: 起初没有看懂，特别绕，简化下，没有别的DT以食物的生物带有可以传染给人类的别的bacteria.提干的结论是the number of ticks acquiring the bacterium―and hence the number of people contracting Lyme disease—would likely decline,围绕的是lyme disease的bacterium，跟other B么有什么关系。

不知道对不对，请给出正确答案

-- by 会员 peter3008 (2010/10/19 10:49:16)

我选的C
理由：A和D不说了
B：这个其实是在说加强Lyme disease is caused by a bacterium transmitted to humans by deer ticks.我觉得这是前提假设，不能这么加强。而且，这个也只是加强了人们得病会减少这个结论，并没有加强DT会减少的结论
C:每个虫子只吃一次。那么别的多了，吃到infected WM的机会就少了，加强
D:我觉得说事削弱或者无关都行，比如说，一个host可以feed很多DT，那么即使other species多了，也不能保证哪些DT不会得病。因为可能很多DT都趴到一个WM上啃。
请NN指点~

eshopaholic

我选D，C明显是削弱的

peter3008

估計樓主都忘了

熊熊加小怪

选B吧。。。
加强得嘛~加强结论说the number of people contracting Lyme disease—would likely decline.

B 排除他因了，people不得从那个带细菌的mice那感染~~~

夜黑风高

正确答案应该是C  ManhattanGMAT 的官方解释 说得很好 可以细致体味一下这个思路

The first step to correctly strengthening or weaking a CR argument is to properly identify the conclusion. In this case the conclusion is easily identifiable due to the indicator word "therefore." Thus, the conclusion is the entire final sentence. To strengthen this conclusion, we must support the contention that the number of people contracting Lyme disease would actually decline by increasing the population of other species on which the larvae of deer ticks feed. Use a Strengthen/Weaken Slash Chart to assess each answer choice individually.

A. Ticks do not suffer any adverse consequences from carrying the bacterium that
causes Lyme disease in humans.
-Irrelevant. The conclusion is about the number of humans that contract Lyme Disease

B. There are no known cases of a human’s contracting Lyme disease through contact
with white-footed mice.
-Irrelevant. The argument never suggests that the mice can directly infect humans.

C. A deer tick feeds only once while in the larval stage.
-Strengthen. If the larvae of a deer tick only feeds once and there are more potential uncontaminated food sources for the larvae, this supports the contention that fewer ticks would acquire the bacterium and thus infect fewer humans.

D. A single host animal can be the source of bacteria for many tick larvae.
-Weaken/Irrelevant. If anything, this answer choice suggests that multiple deer ticks can acquire the bacteria from one mouse. This definitely does not strengthen that FEWER humans would be infected.

E. None of the other species on which deer tick larvae feed harbor other bacteria that
ticks transmit to humans.
-Irrelevant. This answer choice is outside the scope of the argument. The conclusion is specifically about Lyme Disease rather than "other bacteria".

The credited response is C

eshopaholic

你的版本和楼主的版本好像不一样吧，C/D 选项不同。

mofell

楼主你这题是哪里的啊。。
搜遍了CD这个版本也就你这里出现过
特别是那个C选项

好像就没有正确的答案