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.D
E. Psychological treatment of mental illness is not as effective as is medical treatment.
题目不是说immune-system activity 低的人在测试中的成绩低，研究员的结论就是the immune system protects 对于mental illness 和 physical disease 的作用是一样的。题目问研究员的结果是依据下面那个假设的？
那我就觉得结果应该是B呀，为什么答案是D，D是怎么退出来的
| 
