Researchers took a group of teenagers who had never smoked and for one year tracked whether they took up smoking and how their mental health changed. Those who began smoking within a month of the study’s start were four times as likely to be depressed at the study’s end than those who did not begin smoking. Since nicotine in cigarettes changes brain chemistry, perhaps thereby affecting mood, it is likely that smoking contributes to depression in teenagers.

Which of the following, if true, most strengthens the argument?

1. Participants who were depressed at the study’s start were no more likely to be smokers at the study’s end than those who were not depressed.

2. Participants who began smoking within a month of the study’s start were no more likely than those who began midway through to have quit smoking by the study’s end.

3. Few, if any, of the participants in the study were friends or relatives of other participants.

4. Some participants entered and emerged from a period of depression within the year of the study.

5. The researchers did not track use of alcohol by the teenagers.

参考答案选A，我很不解。A是weanken了原argument，那么取反是否support原argument呢？

Argument想表达的就是：吸烟导致青少年神情压抑。

A取反是：那些已开始便神情压抑的参与者要比一开始不神情压抑的参与者在最后更容易成为吸烟者。

这是在说depressed作用于smoke，而不是smoke会作用于depressed，并没有支持argument呀？

答案应该是A。

A排除了压抑促使参与的志愿者更可能去抽烟。从而支持是抽烟导致压抑，而不是压抑导致人更多的吸烟。