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?
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.
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.
Few, if any, of the participants in the study were friends or relatives of other participants.
Some participants entered and emerged from a period of depression within the year of the study.
The researchers did not track use of alcohol by the teenagers.
A.属于排他因型加强,这里的他因是因果倒置的情况
文中说因为吸烟和抑郁这两件事有关系,所以吸烟导致抑郁
而反驳可以说其实是抑郁导致吸烟,所以它们两才有关系。
而A就是排除了这个反驳的情况,说抑郁的人才不会更容易吸烟呢,其实就是加强了结论。
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