Its no longer a question now whether man can land on the moon.这句话有误吗

It's no longer a question now whether man can land on the moon.

这句话有误吗？是不是应改为that引导主语从句，为何？

It's no longer a question now whether man can land on the moon.

这句话是正确的。It 是形式主语； whether（是不是） man can land on the moon 是主语从句。