It’s no long a question now men can land on the moon. A. that B. whichC. whether D. what

问题补充：

It’s no long a question now men can land on the moon.

A. that

B. which

C. whether

D. what

答案：

(答案→)A. that

B. which

C. whether

D. what

解析：It在句子中作形式主语，that引导的从句充当真正主语。