Bob could have seen the famous pop star yesterday morning.
A. did he e
B. if he came
C. had he e
D. if he should e
网友回答
A. did he e
B. if he came
(答案→)C. had he e
D. if he should e
解析：考查虚拟语气和倒装。在条件句中，表示与过去事实相反的虚拟语气时，条件句中使用过去完成时的时态。如果省略了if可以把had提前形成部分倒装的形式。本题的had he e yesterday morning=if he had e yesterday morning。