OG-------83,请教，谢谢先！

83 Any medical test will sometimes fail to detecta 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的解释：
Only choice C, the best answer, produces a sentence in which every pronoun it refers clearly and logically to the noun condition. In choices A and B, the phrase indicate that there . is one does not grammatically fit with when it is not because it has no referent. Choices B and D are imprecise in saying that a test will fail to detect when a condition is present, since the issue is the presence and not the timing of the condition. Further, its presence in D leaves the it in when it is not without a logical referent: it must refer to condition, not presence. Choice E repeats this error; also, the presence ... when it is there is imprecise and redundant

a b选项，解释说it 没有指代对象，可我觉得前面的one就是它的指代对象，因为one 明显是指 a condition.
请大家指教！
[em07]