问题
选择题
________ your letter, I would have set off two days ago.
A．If I could have received
B．Should I receive
C．If I received
D．Had I received
答案
答案：D
D 考察虚拟倒装，根据题干，本题表示与过去事实相反，从句部分使用过去完成时，从句中中有had，可以省略if并把had提前构成虚拟倒装。