问题
选择题
_____ in the queue for 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
答案：C
考查非谓语动词。句意：已经在队列里等了一个小时，汤姆突然意识到他把钱包忘在家里了。现在分词表示正在进行的伴随性的动作，其逻辑主语是句子的主语，如果分词动作发生在主语动作之前，则要用完成时态的现在分词，故选C。