It is no longer a question nowman can land on the moon A．that B．if C whether D what

问题补充：

It is no longer a question nowman can land on the moon．

A．that B．if C whether D what

答案：

解析：

it这里是形式主语，that 后面是实际主语，人类到达月球现在已不再是问题了。