The reason for his success is he worked very hard.A. whyB. thatC. whetherD. how

问题补充：

The reason for his success is he worked very hard.

A. why

B. that

C. whether

D. how

答案：

A. why

(答案→)B. that

C. whether

D. how

解析：名词性从句考查题。That连接表语从句不做成分不能省。句意：他成功的原因是他工作努力。