请问这道数学题是什么意思啊？

Q35:
For what percent of those tested for a certain infection was the test accurate; that is,
positive for those who had the infection and negative for those who did not have the
infection?
(1)   Of those who tested positive for the infection,   did not have the infection.
(2)   Of those tested for the infection, 90 percent tested negative.

答案选E，我没怎么看懂，请哪位解释一下可以吗？非常感谢！

我感觉答案也是E

positive for those who had the infection and negative for those who did not have the
infection?这一句只是说明什么是positive和negetive，至于是否accurate不知道。

求的是accurate percent

条件1说positive的accurate，但是没有说negetive是否accurate

条件2说90%nagetive，可以求出10%positive

两个条件合在一起只能求出positive的accurate percent。negetive的不知道