问题
选择题
_____in the queue for half an hour，the old man suddenly realized he had left the cheque in the car.
A．Waiting
B．To wait
C．Having waited
D．To have waited
答案
c
C考查非谓语动词的用法。根据the old man与wait 之间的关系，应该选择。.一ing形式；再根据句意可知，老人是在主句谓语动词“realized”前就“等了(wait)半个小时“，有明显的先后关系.故要用v一ing形式的完成式。