求教OG17最后一题weaken question

刚柔始交而难生

It is widely assumed that people need to engage in intellectual activities such as solving crossword puzzles or mathematics problems in order to maintain mental sharpness as they age. In fact, however, simply talking to other people—that is,participating in social interaction, which engages many mental and perceptual skills—suffices. Evidence to this effect comes from a study showing that the more social contact people report, the better their mental skills.
Which of the following, if true, most seriously weakens the force of the evidence
cited?
(A) As people grow older, they are often advised to keep exercising their
physical and mental capacities in order to maintain or improve them.
(B) Many medical conditions and treatments that adversely affect a person’s
mental sharpness also tend to increase that person’s social isolation.
(C) Many people are proficient both in social interactions and in solving
mathematical problems.
(D) The study did not itself collect data but analyzed data bearing on the
issue from prior studies.
(E) The tasks evaluating mental sharpness for which data were compiled by
the study were more akin to mathematics problems than to conversation.
OA:B。
explanation: B Correct.   This provides evidence that the correlation observed in the study results from mental sharpness facilitating social interaction, in which case the study results do not indicate that social interaction facilitates mental sharpness。
下面是我的理解
Premise:社交增加会导致头脑更加敏锐。
Conclusion:参与社交活动就足以使头脑保持敏锐。
GAP：社交活动和头脑敏锐之间没有必然的因果练习，也可能是头脑敏锐的人喜欢参加社交活动。
B选项：头脑迟钝会增加社交孤立。
社交用S来表示，头脑用M来表示。
premises是S+和M+同时发生，结论是S+->M+.
按照答案的解析，能够weaken的应该是M+->S+,但是B选项给的是M-->S-，你们不觉的B选项和它对B的解释之间还存在一个巨大的GAP吗？
M-->S-是不能推出M+->S+的啊。

熊先生

被你的符号绕晕了... 我对这道题也有疑问，思考后想法是这样的。

B之所以正确，是因为它提到的treatments证明了mental sharpness对social interaction有促进作用，但没有treatments说明了后者对前者有促进作用，所以削弱了这个evidence的force。

反而是E选项，根本读不明白…