知道的说一下，最好能举一些例子，拜托拜托！！！！！！！！！
热心网友
过去完成时表示某动作/情况发生在过去某时间之前。即“过去的过去”。如：He had worked in a car factory for three years before he came here.他来这儿前在一家汽车厂工作了三年。I had finished my experiment when I went out to play.我出去玩时已做完了实验。
热心网友
had+过去分词，用法和现在完成时基本一样。例如，I had finished my homework 2 hours ago.