GWD 6-13

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 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?

1. Ticks do not suffer any adverse consequences from carrying the bacterium that causes Lyme disease in humans.

2. There are no known cases of a human’s contracting Lyme disease through contact with white-footed mice.

3. A deer tick feeds only once while in the larval stage.

4. A single host animal can be the source of bacteria for many tick larvae.

5. None of the other species on which deer tick larvae feed harbor other bacteria that ticks transmit to humans.

我选了B，可是答案是C。因为我认为没有人直接接触white-footed mice而生病的案例，说明white-footed mice是唯一的途径，去掉了这个可能性，那么减少deer tick 与white-footed mice的接触就可以减少病例。可答案是C。deer tick 在幼虫阶段只吃一次，so what? 大家探讨一下！

句子里的观点是：deer ticks只有在吃white-footed mice的时候，才会pick up致病细菌；吃其他的物种，都不会harbor致病细菌。因此，建议增加其他物种的数量。

C选项是幼虫只吃一次，这么理解：如果幼虫吃好几次，那么其中吃到一次两次white-footed mice的几率就会比较大，还是容易传染给人类。如果只吃一次，我们增加其他物种，幼虫可能就碰不到white-footed mice，从而使得得病的人也少了。

另外，我觉得B选项没有加强观点，而只是加强了deer ticks携带致病菌的证据。因为观点是增加其他物种数量。