When people engage in activities that help others, their brain releases endorphins, the brain’s natural opiates, which induce in people a feeling of well-being. It has been suggested that regular release of endorphins increases people’s longevity. And a statistic on adults who regularly engage in volunteer work helping others shows that they live longer, on average, than adults who do not volunteer. However, that statistic would be what we would expect even if volunteering does not boost longevity, because___________ Which of the following most logically completes the argument? A In the communities studied, women were much more likely to do regular volunteer work than men were, and women tend to live longer than men do B The number of young adults who do regular volunteer work is on the increase C The feelings of well-being induced by endorphins can, at least for a time, mask the symptoms of various conditions and diseases, provided the symptoms are mild D It is rare for a person to keep up a regular schedule of volunteer work throughout his or her life E Some people find that keeping a commitment to do regular volunteer work becomes a source of stress in their lives 错选了C，答案给的A。A说女士比男士更可能做志愿活动，女士比男士活得长。这不是支持原文了么？可以题目不是应该驳斥吗？

【请May老师回答】这题鸡精提供的答案是D 可是我觉得第二个条件不能得出呢 假设n三次方是x平方 除以n平方 是可以得到x/ n 平方 但是x/n 不一定是整数呀？

7.15/寂静：STUVW, 5个人， V和W中间必须隔一个人，求问共有几种组合？ 我的想法是这样的A（3,3）*A(2,2)*C(3,1)=36种；思路如下：先把V+C(3,1)+W看成一个整体；可得：A(2,2)*C(3,1)种排法；然后5个人可分成三类，于是A(3,3)。不知道我的想法对不对，请老师解答。感激不尽！

急求此题！谢谢老师！题目来7/6自寂静。x∈{1, 2, 3}，y∈{4,5,6}，z∈{7,8,9}，求yxx与z的乘积为偶数的概率？我根据求反可得：2/3x1/3x2/3=4/27 1-4/27=23/27 不等于5/9呀？我就是卡在这里了求教。谢谢！

请郭老师看一下这几题 谢谢老师

麻烦郭老师看一下这几题，谢谢老师

麻烦郭老师看一下这几题，谢谢

请郭老师帮我看一下这几道题，好几个都完全不会…

请郭老师帮我看一下这几道题，好几个都完全不会…

不是很明白为什么A选项不对 我觉得outnumber了给其他人写信的数量可以作为这个period Emily写信的结果出现 为什么不能用现在分词呢？