OG-48

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.

解释说 If, contrary to D, mental illness can depress immune-system activity, the association mentioned does not support the researcher's conclusion. So D must be assumed.

看完解释后还是不明白，mental illness不导致immune-system activity降低与题目中说到的情况好象没什么关系。

查询以前的讨论帖子，有位NN提到“这是典型的 A causes B.    assumption： 不是B causes A 的题型。做多了就明白了。”可我还是不明白这种题型做法，有哪位NN帮忙进一步解释一下，并指导一下如何对付这种题型。

多谢！