.过去完成时用法小结一、过去完成时适用场合1. 过去完成时表示在过去某一时间或动作以前已经完成了的动作。这个过去的时间常用by，before等介词短语或一个时间状语从句表示，也可以暗含在上下文中。I had finished my homework before supper.我在晚饭前就把作业做完了。The play had already started when we got to the theatre. 我们到剧场时戏已经开始了。 By the end of June they had treated over 10,000 patients. 到六月底他们已经治疗了一万多病人。2. 过去完成时还可表示过去某一时刻之前发生的动作或状态持续到过去某个时间或还要持续下去，常与for，since等词连用。如：He had served in the army for ten years before he retired last year. 他在部队干了十年，去年退役了。He told me that he had known
