标题: 这一题居然选A？大家怎么说？ [打印本页] 作者: frankzhiwei 时间: 2010-11-18 22:08 标题: 这一题居然选A？大家怎么说？ 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.
要证明1），必须排除2）作者: kevin0214 时间: 2010-11-18 22:21
明显地排除他因。排除B导致A的可能性，支持了A导致B。作者: jake1 时间: 2010-11-18 23:36
A项保证了前提，因此加强了结论。作者: sdcar2010 时间: 2010-11-19 01:47
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.作者: ArsèneSONG 时间: 2017-3-5 09:48
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