The maths problem is so hard.I really don't know ______.

问题描述:

The maths problem is so hard.I really don't know ______.
A how to do it.B how to do.C what to do it.选哪个?为什么?

Ahow to do it 如果没有it 那就缺少宾语啊
你应该把what to do 和那个弄混了what to do没有it 是因为what本身就可以做宾语