There is no doubt he will succeed.A. whetherB. whichC. thatD. if

问题补充：

There is no doubt he will succeed.

A. whether

B. which

C. that

D. if

答案：

A. whether

B. which

(答案→)C. that

D. if

解析：考查同位语从句，同位词是doubt，that引导同位语从句，起连接作用，不做成分，句意：毫无疑问他会成功的。选C。