关于定语从句介词放置小问

Donquioxte

A recent poll of elected officials suggests that candidates, when in themidst of a tough campaign, often make statements about an opponent thatthey may not think is true.

(A) is

(B) are

(C) to be

(D) of as

(E) it is

这里的D选项的错误，是否是这样理解的 think of the statements as在这里statements做的事介词后面的宾语所以前面的that必须用which替换？

我又一想如果是一句正确的定语从句那么of 是否必须提到which前面，即 candidates often make statements of which they may not think as true.或者放在句子中也是可以的？顺便问一句of which前需要加逗号么？

最后正确答案是B，C选项为什么错呢？

求大神解答！

Donquioxte

防沉！！自己顶