I have no idea it is that makes him puzzled.A. howB. whatCwhyD. which

问题补充：

I have no idea it is that makes him puzzled.

A. how

B. what

Cwhy

D. which

答案：

A. how

(答案→)B. what

C. why

D. which

解析：词义辨析。A. 怎样 B. 什么C.为什么 D.哪一个。句意：我不知道是什么让他迷惑不解。从句缺少主语，故选B。