83. 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

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.

句意不明白，不理解句子的意思。

所以解释也看不懂。

求大家帮忙！

就是medical test有时候颠倒黑白，检查不到存在的condition,或者把

本来不存在的condition又说成存在。

我的理解哦,这句话的意思大概是这样的: 任何一个医学实验有时都回

漏掉这样一种情况, 那就是: 当他出现时, 那些医学实验回说他没有出现.

其实就相当于比如一个人确实得了癌症, 但是某些医院的检查结果是阴性

的(没有得),或者那个人根本没有的癌症, 可是有的医院的检查结果却是阳

性(得了)

BDE很明显是错的. 在A 中, 用了一个泛指的One, 又用了一个特指的it,

在一个句子中, 用了泛指就不能用特指, 所以排除A, 选C