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 ilness as well as against physical disease.

The researcher's conclusion depends on which of the following assumption??

答案是 D  Mental illness does not cause people's immune-system activity to decrease.

題目都說 low levels of immune-system activity 會造成 lower score on tests of mental health，為何結論還會建立在

"Mental illness does not cause people's immune-system activity to decrease" 的假設上？？

'coz both kinds of people have the same chance to get mental illness, but the people having higher level of immune system activity tend to get over it better than the people with lower level of that.

which is based on the assumption: Mental illness does not cause people's immune-system activity to decrease.

If mental illness does cut down the immune-system activity as AIDS does, they will score the same.

那为什么B不对呢??

取非也可以削弱原文啊

不懂,请教各位

顶上来看

A="low level of immune-system"

B= "lower mental health"

A = “normal or high immune-system” = non-A

B = “normal or high mental health” = non-B

A researcher discovered that “A has association with B. “

The researcher concluded that “non-A will lead to non-B”. (which is equal to “B lead to A”)