the problem is too difficult for us to work out中的work out为什么中间不用it

问题描述:

the problem is too difficult for us to work out中的work out为什么中间不用it
什么时候要加it
so that?还是别的句子

主语已经是the problem,work out就是指它的
如果是这句话the problem is so difficult that we can't work it out中就要加了,因为这是从句,that后面的主语是we,所以就要加了