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 免疫力高的人比免疫力一般的人更能防止自己得精神疾病 没有比较高和一般 无关
B 讨论的是mental illness 和 physical disease 无关
C 免疫力高的人不会得精神疾病，然后呢？低的人怎么样 没有提到
D 精神疾病不会导致人的免疫力变低，排除了得精神疾病导致免疫力下降的可能性，说明确实是低的人得精神疾病的几率要高些 正确
E 比较治疗方法 无关
for the passage, we can analyse as following: ‘who have low levels of immune-system activity tend to score much lower on tests of mental health ’ Correlation: lower immune-system activity ~ lower possibility of mental illness. 'the immune system protects against mental illness as well as against physical disease.' Cause and effect relationship: The immune system cause low possibility of mental illness and the physical illness. We should eliminate that the orientation is the immune-system to mental illness but not the mental illness to the immune-system. So choice D is correct. C is the repeated conclusion of the argument.