85. 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 Grammatical construction
In this sentence the pronoun it does not always refer to condition,and,for the sake of clarity and correctness,it must.Detect a condition when it is present is correct and should be followed by a corresponding construction:indicate that it is present when it is not.The construction of there isone leaves it without a referent. AThere is one leaves it in the final clause without a referent. B Detect a condition is more precise because it emphasizes the condition itself;there is one leaves it without a referent. CCorrect.The three uses of the pronoun it refer clearly to condition,and the two parts of the sentence correspond. DWhen a condition is present emphasizes the time of the detection rather than the condition itself;the final it has no referent. EPresence illogically repeats the same idea as when it is there, the final it has no referent. The correct answer is C.
不明白A的解释是什么意思,“there is one”会导致句末的it指代这里的one,而不是前面的condition吗?