He will have to stay in hospital.That’s what he____

问题描述:

He will have to stay in hospital.That’s what he____
a has done b must do c must be doing d must have done
为什么C不对呢

will have to do表示将不得不做,但最终还未做,所以回答的时态也要和前句一致,
A为现完,已做过,B必须做,还未做,C一定正在做,D肯定已经做过