There is no doubt he will finish the task in time.A. ifB. whetherC. whatD. that

问题补充：

There is no doubt he will finish the task in time.

A. if

B. whether

C. what

D. that

答案：

A. if

B. whether

C. what

(答案→)D. that

解析：句意,无疑他会按时完成这项任务。there is no doubt 句型中当doubt本身被否定时，其后跟的宾语从句或同位语从句应用that引导；doubt被肯定时，其后的宾语从句用if或whether引导，同位语从句则由whether引导，不能用if引导。故选D.