48. A researcher discovered that people who have low levels of immune-system activity tend to score much lower on tests of mental health than do people with normal or high immune-system activity. The researcher concluded from this experiment that the immune system protects against mental illness as well as against physical disease.
The researcher’s conclusion depends on which of the following assumptions?
A. High immune-system activity protects against mental illness better than normal immune-system activity does.
B. Mental illness is similar to physical disease in its effects on body systems.
C. People with high immune-system activity cannot develop mental illness.
D. Mental illness does not cause people’s immune-system activity to decrease.
E. Psychological treatment of mental illness is not as effective as is medical treatment.
想请教前辈们如何解此题，不是很懂？另外，可否请大家帮我翻译，感激！！
Sorry that I cannot type Chinese as fast as English, not even close. So I have to answer in English, as usual. I do not think it is necessary to translate as you need to learn to work on GMAT this way.
I think I see your post on the other section. I believe that you need to focus on the structure of reasoning. Also you need to know assumption is required condition, which has to be true for a conclusion to be true. For example: All human have intelligence. Conclusion: Tom has intelligence. The assumption is that Tom is human. If the assumption is not true, the conclusion is not true.
In this question, the conclusion is that immune system protects people from mental illness. The supporting evidence is that people with low immune system tend to have mental illness. That is all the factors in this argument.
You can see that the conclusion is drawn because two factors coexist: low immune system and mental illness. The causal relationship is "Immune system --> mental illness". In order for the conclusion to be correctly drawn, D has to be right. Or if D is not true, say mental illness causes lower immune system, the causal relationship is reversed. Thus the conclusion will not be true.
我在看OG的解释的时候, 正好就是对mindfreeGG的这段逻辑分析感到很疑惑…
选D的原因是因为: “当两件事之间存在因果关系时, 假设A推导出B,
若能证明事实为B推出A, 则原本的假设不成立”...
此题由于若D不正确的话, 即: mental illness 可抑制免疫系统, 违背原题结论, 因此推出D是正确的…
我的问题在于:
1. 为什么A推出B, B就一定不能推出A呢? 两者不能互为因果吗?
2. 就算第1点成立, 也不表示B不能推出A, B的相反就一定可以推出A啊? (因为 “mental illness 可抑制免疫系统” 违背原题结论, 所以推出其相反 “mental illness 不会抑制免疫系统” 就是原题的assumption…)
越来越混乱了… 救命啊~~!
1。因果的意思为A引起B，既然是一个引起另一个，就是一个发生在先，一个发生在后。如果是相互引起，你说那个在先。当然，不同场合那就不同了。
2。假设是原文结论的必要条件，所以它错，原文结论必推不出，必错。假如D是错的，Mental illness does cause people’s immune-system activity to decrease。则Mental illness 是因，后者是果。既然如此，就不可能Mental illness 是果了。结论推不出。
啊…. 最后一句很重要, 我是把因果关系跟充分必要关系搞混了,
所以虽然正向我懂了, 可是因为觉得反向不合逻辑, 所以整个都拧了….
感谢lawyer-1 gg 清楚的解释~~!
不好意思，所以D选项就是要为了证明心理疾病不会导致免疫系统活动力下降，
可得出immune system activity 是因，然后mental ….是果，而可得文中的结论，是ㄇ？请指教
另外，我想请问mindfree 所说的structure of reasoning，是指我需要熟悉文章中的因果关系ㄇ？！谢谢！
假设是原文结论的必要条件。则原文结论是假设的充分条件。必要条件不成立，充分条件也不成立。所以说假如D是错的，则 Mental illness 是因，immune-system activity to decrease是果。则原文结论immune-system activity to decrease是因，Mental illness 是果就不成立。所以说D是原文结论的假设。
Thanks a lot!! I got it!!!!
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