76.I have no idea__she will be back.为什么这里填when而不填that?

问题描述:

76.I have no idea__she will be back.
为什么这里填when而不填that?

意思是:我不知道她什么时候会回来,可以说:
I have no idea that when she will be back.
that可以省略,when不可以省略,所以只能填when