（）in the queue for half an hour,tom sud denly realized that he had left his wallet at homea:To wait b:Have waited c:Having waited d:To have waited为什么要用having?b,由tom做的动作所以用ing形式?表主动?、请一个一个的解释
问题描述：
（）in the queue for half an hour,tom sud denly realized that he had left his wallet at home
a:To wait b:Have waited c:Having waited d:To have waited
为什么要用having?b,
由tom做的动作所以用ing形式?表主动?、
请一个一个的解释
答
C wait的行为也是由Tom做得,并且两个动作是同时发生的.所以用进行时态的分词.
答
这是个非谓语结构,真正的谓语动词是 realize ,如果表示主动则为 Having done,被动则为 Having been done,意思是后面的这个动作在谓语动词表示的动作之前发生,本题中wait 动作发生在realize前,并且是Tom 主动发出的,故为正解.C 选项这种结构是不存在的,没有to + 完成时这种结构.