OG it指代请教！

haveacigar233

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
B）when a condition is present and indicate that there is one
C）a condition when it is present and indicate that it is present
D）when a condition is present and indicate its presence
E）the presence of a condition when it is there and indicate its presence

OG对五个选项都解释说最后没有划线的那个it在5个答案中都没有referent。我理解逻辑上所有选项的its/it都指代的是condition啊，难道是什么语法上的错误造成没有referent？还是产生歧义了会指代别的词？请指点！

OA是C

haveacigar233

其实就是 我觉得it的指代是清楚的，不知道为何不清楚。。。。