冒冒爱雨雨
1、现在完成时：指到现在为止这个动作已经完成。例如：I have finished the project. 项目目前是完成状态。2、过去完成时：指到过去某个时间点已经完成。时间状语：before, by the end of last year(term, month…),etc. 基本结构：had + done. 否定形式：had + not + done. 例如：I had collected one hundred stamps by the end of last year。（到去年底已经··）3、现在完成进行时：到现在为止一直进行着··例如：I have been working on this lab since last month but have not finished yet.我从上个月就一直在做这个实验但是到现在还没完成
