It is true of both men and women that those who marry as young adults live longer than those who never marry. This dose not show that marriage causes people to live longer, since, as compared with other people of the same age, young adults who are about to get married have fewer of the unhealthy habits that can cause a person to have a shorter life, most notably smoking and immoderate drinking of alcohol.

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

1. Marriage tends to cause people to engage less regularly in sports that involve risk of bodily harm.
2. A married person who has an unhealthy habit is more likely to give up that habit than a person with the same habit who is unmarried.
3. A person who smokes is much more likely than a nonsmoker to marry a person who smokes at the time of marriage, and the same is true for people who drink alcohol immoderately.
4. Among people who marry as young adults, most of those who give up an unhealthy habit after marriage do not resume the habit later in life.
5. Among people who as young adults neither drink alcohol immoderately nor smoke, those who never marry live as long as those who marry.

why D?不懂啊郁闷死了,大家帮忙!

这道题我用排除法做的，题干说的是young adults结婚活得长，备选答案只有D和E提到young adults, 和题干所表达的主语范围一致，而ABC都没有提到young adults, 即使有结婚能使人长寿的意思也不是most strengthen的答案；而D和E中，很显然只有D有加强作用，完全符合题干young adults结婚长寿的意境。

不知道大家还有什么更好的推理方法？