They are good friends.is no wonder that they know each other so well.A. ThisB. ThatC. Ther

问题补充：

They are good friends.is no wonder that they know each other so well.

A. This

B. That

C. There

D. It

答案：

A. This

B. That

C. There

(答案→)D. It

解析：通过分析句子结构，可知这个句子中包含一个主语从句，而主语从句位于句末，故需要It作形式主语，只有It可以作形式主语。