Question

________ in the queue for half an hour, Tom suddenly realized that he 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：

分词作状语。wait和逻辑主语Tom之间是主谓关系，要用现在分词waiting。“已经等了半个小时了才想起来……”，因此用完成式。