2015年职称英语考试已经开始备考,本阶段应该多整理一些基础词汇和语法。为此,医学全在线职称外语频道特整理了“2015年职称英语备考语法资料”供您参考,希望对您有帮助!
(7)过去完成时表示过去某一时间或某一动作发生之前已经完成的动作。简言之,过去完成时所表示的时间是“过去的过去”。
①过去完成时由“助动词had+动词的过去分词”构成。
②过去完成时时间状语有:by(yesterday),by then,by the end of(last…)或者由when,before等引出状语从句。有时句子中会有already,just,once,ever,never等词语,也会有for… 或since…构成的时间状语。如:They had already finished cleaning the classroom when their teacher came.(当老师来的时候他们已经打扫完了教室)/ The woman had left before he realized she was a cheat.(在他发觉那个妇女是个骗子时她已经走掉了)
③过去完成时常用于宾语从句中、after引导的从句中,或者从句是before引导的主句中。如:After I had put on my shoes and hat,I walked into the darkness.(我穿上鞋子戴上帽子走进了黑暗之中)/ He said that he had never seen a kangaroo before.(他说他以前从来没有见过袋鼠)