[请教]OG-83

归零

OG-83

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

关于it指代的问题，看了解释还是糊涂，请高人指点。这种类型的题目该如何思考。

谢

1stzhang

这个题目要从并列入手，从划线的地方是没有突破点的。when it is not这个省略结构表示前面的主句肯定有it is ....这个结构。有的只有C,这个题目什么没考，就考了一个平行结构。我觉得语法考到最后就是考眼神了