[讨论]

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 strengthen the argument?

Ø       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.

Ø       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.

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

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

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

第一次发贴，如果不规范请多指教。看了前面只有一个帖子讨论该题，我觉得A也有问题。文章中实验的方法是说追踪那些头一个月之内抽上烟的人在实验结束时郁闷的情况，而A说      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. 实验结束时才成为抽烟者的人应该不是实验观察的对象啊。该题需要仔细考虑时间状语的问题吗？反倒认为B对