Bob could have seen the famous pop star yesterday morning.A. did he comeB. if he cameC. h

问题补充：

Bob could have seen the famous pop star yesterday morning.

A. did he come

B. if he came

C. had he come

D. if he should come

答案：

A. did he come

B. if he came

(答案→)C. had he come

D. if he should come

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 come yesterday morning=if he had come yesterday morning。