[求助]白勇语法P43页第51题不明白

51. 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

选 C

理由：AB 选项 indicate there is one when it is not 中，状语从句when it is not 省略的表语无法还原，也就是说状语从句不能按照语法要求承接there is one省略。

我不明白什么叫做‘不能按照语法要求承接there is one省略’？

有没有更好的说法来解释呢？

谢谢！