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

问题补充：

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

答案：

解析：考查现在分词的完成式用法：通过分析句子，后面是主句，前面是分词做状语，因为句意是：排队等了半小时后，汤姆突然意识到他把钱包落在家里了。说明是先等了半小时才发现的，状语和主句的动作有明显的先后关系。用现在分词的完成式。选C。

考点; 考查现在分词的完成式