请教NN一道逻辑, thank you!

turtlecat

不明白为什么答案布是B确是D? 前提的测试没提到身体的疾病啊?

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.
            (D)

    (e)  
Psychological
treatment of mental illness is not as effective as is medical treatment.

紫苏

assumption题目有一部分可以把答案取非，如果能削弱就是答案。

LZ再想先

turtlecat

Thank you 紫苏 . Based on the rule of 把答案取非，如果能削弱就是答案, the answer makes sense, however, I feel the "physical
disease" is a flaw. Very confusing...
Thank you again for helping me!