it is still under discussion whether the old bus station should be replaced with a modern hotel or n

题目

it is still under discussion whether the old bus station should be replaced with a modern hotel or not为什么是主语从句?

答案

it is still under discussion（that） whether the old bus station should be replaced with a modern hotel or not.前办部分it是形式主语,真正的主语是that后面的从句.可以用后面的从句替代it的....