A study comparing a group of chronically depressed
individuals with an otherwise matched group of
individuals free from depression found significantly
more disorders of the immune system among the
depressed group. According to the researchers, these
results strongly support the hypothesis that mental
states influence the body's vulnerability to infection.
Which of the following, if true, casts the most seri-
ous doubt on the researchers' interpretation of their
findings?
(A) The researchers' view does little more than echo
a familiar theme in folklore an literature.
(B) Chronically depressed individuals are no less
careful than others to avoid exposure to
infections.
(C) Disorders of the immune system cause many of
those individuals who have them to become
chronically depressed.
(D) Individuals who have previously been free from
depression can become depressed quite
suddenly.
(E) A high frequency of infections can stem from
an unusually high level of exposure rather
than from any disorder of the immune system.
答案是C，我选的是E。不知题目是怎样推出来的？ | 
