I’m sorry Andy didn’t want to go to the conference.willing to go

问题描述:

I’m sorry Andy didn’t want to go to the conference.willing to go
I’m sorry Andy didn’t want to go to the conference. ________ willing to go we would have paid all his expenses.
A) Being
B) Was he
C) He had been
D) Had he been
答案是D 为什么不是A?总觉的选D有点不通

省略了if 的倒装的虚拟语气的用法