这一题居然选A？大家怎么说？

frankzhiwei

A study followed a group of teenagers who had never smoked and tracked whether they took up smoking and how their mental health changed.After one year, the incidence of depression among those who had taken up smoking was four times as high as it was among those who had not.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?



A. Participants who were depressed at the start of the study were no more likely to be smokers after one year than those who were not depressed.

B. The study did not distinguish between participants who smoked only occasionally and those who were heavy smokers.

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

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

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

题目是说吸烟---脑袋、化学物质----影响心情
可是A是说开头就depressed的人不会更容易吸烟，不仅不大相关，感觉因果翻过来了呀~还是我没读懂呢？

求教，感谢~

eshopaholic

已有信息说明，吸烟和情绪低落相关

有两种可能：1）吸烟导致情绪低落 ； 2）因为情绪低落，所以抽烟

要证明1），必须排除2）

kevin0214

明显地排除他因。排除B导致A的可能性，支持了A导致B。

jake1

A项保证了前提，因此加强了结论。

sdcar2010

Of course the answer is A. If one who depresses tends to smoke, then the whole argument falls apart. Correlation and causation are the favorite subject for GMAT test makers.

ArsèneSONG

NS   =   不吸烟者     S    =    吸烟者     ND   =   不抑郁者   D  =  抑郁者
假设样本数量为20. 根据题目中的 4倍关系，as 4 times as high,得到下表左边。
根据A选项，no more likely（假定为1/4），得到下表右边。
NS       S         D                          ND      D        S
20     ——      16        实验组         4     ——       1
——     20       4         对照组        ——    4         1

根据右表的1/4 关系，可知在NS组16个抑郁的人当中有16*1/4=4个是原发型抑郁，则有16-4=12个吸烟诱发型抑郁。
而在S组中，则有4*1/4=1个原发型抑郁，4-1=3个吸烟诱发型抑郁；
对比以上两个结果，两组人数相同的情况下，第一组确实比第二组吸烟诱发型抑郁人数多，因此加强结论。
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然而考场上千万不要这么做。

lisiberry

这是道强化题，因为条件本身有个漏洞。
论点是，虽然实验结果是吸烟的人显示更大的压力，因此我们说吸烟增加压力。
漏洞是，如果实验结果中学会吸烟的人是实验前就有很大的压力的人，我们就无法得出吸烟会增大人的压力。而是本来这些人就有压力，无关吸烟。因此会导致论点失败。

A排除了这个漏洞，所以正确。