The reason why he succeeded is he worked very hard.A. whyB. thatC. whetherD. how

问题补充：

The reason why he succeeded 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：考查表语从句that在从句中不做成分只起连接作用没意思。句意：他成功的原因是他工作非常努力。