He must have had an accident,or he _A_ then.A would have been here B had to be here C should be here D would be here为什么?

He must have had an accident,or he _A_ then.A would have been here B had to be here C should be here D would be here为什么?
He must have had an accident,or he _A_ then.
A would have been here B had to be here
C should be here D would be here
为什么?

He must have had an accident,or he _A_ then.A would have been here B had to be here C should be here D would be here为什么?
A,表虚拟现实,如果不是这样（车祸）的话,他应该在那里的!

虚拟语气的。 前面是过去完成时的推测、 后面也应该用过去完成将来时 、 OK

A
要用have，应为是过去时