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
网友回答
A. If I could have received
B. Should I receive
C. If I received
(答案→)D. Had I received
解析：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。