求助：白勇语法第二章第50题

tanyawu

白勇语法第二章第50题

Any medical test will sometimes fail to detect a condition when it is present and indicate that there is one when it is not.

A a condition when it is present and indicate that there is one
C a condition when it is present and indicate that it is present

请问A和C比较为什么要选C? 白勇的批注看不太明白。

tanyawu

对噢，说得有道理！