ITS的指代问题,OG83和0G60,进来看看

OG83
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 presenc
answer:C
请看解释: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

为什么说D和E中的IT 指代有问题,its presence "its "指代condition,"it" in when it is not 也指代condition,有什么问题吗? 现在很疑惑its指代的用法,象OG的60题:60. According to a recent poll, owning and living in a freestanding house on its own land is still a goal of a majority of young adults, like that of earlier generations.
(A) like that of earlier generations
(B) as that for earlier generations
(C) just as earlier generations did
(D) as have earlier generations
(E) as it was of earlier generations

ITS和IT的指代也不是同一对象,不知道是什么语法点,请指教.

不好意思，看了还是不太明白

还是83的问题 ，既然IT没有就近指代的规则，那么解释中的it可能指代presence，怎么理解

菜鸟语法说，就是考的代词的就近指代。

再说5个选项中，when it is not 都是由and引起的另一个分句的从句，it不可能跳跃到and前的另一个分句里指代吧。

所以：

A，B中，it唯一可能的先行词就是there，不合逻辑。

D，E中，it的先行词都是its presence，中心词是presence，改变了意思。

只有C的指代是正确的：

indicate that it is跟fail to detect a condition平行，所以it指代condition。
递进则有后面未划线部分when it is的it先行词是indicate that it is的it，指代condition

還有一個想法

就是代名詞不能指代所有格

因此it=/ its precence