Question

【题目】

________ in the queue for half an hour, Tom suddenly realized that he had left his wallet at home.

A. To wait

B. Have waited

C. Having waited

D. To have waited

Answer 1

【答案】C

【解析】主句主语Tom和wait存在逻辑上的主谓关系，且时间状语为for half an hour，故用现在完成时的进行式，表主动。