There is no doubt those who work hard will succeed sooner or later.A. ifB. whetherC. whyD

问题补充：

There is no doubt those who work hard will succeed sooner or later.

A. if

B. whether

C. why

D. that

答案：

A. if

B. whether

C. why

(答案→)D. that

解析：考查固定句型，There is no doubt that…意思“毫无疑问…”，句子意思“毫无疑问那些努力工作的人迟早会成功的”