It’s no longer a question now man can land on the moon.A. thatB. whichC. whetherD. what

问题补充：

It’s no longer a question now man 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：考察主语从句。It是形式主语，真正的主语是后面的从句that man can land on the moon,that在句中起连接作用，没有实际的意义。