百度知道 - 信息提示

首先，been 不是必不可少的 1） 概念：表示过去的过去 ----|-------|-----|---->其构成是had +过去分词构成。 那时以前　 那时　现在　　　　　　 2） 用法 　 a.　在told, said, knew, heard, thought等动词后的宾语从句。 　　 She said (that) she had never been to Paris. 　 b. 状语从句 　　 在过去不同时间发生的两个动作中，发生在先，用过去完成时；发生在后，用一般过去时。 　　 When the police arrived, the thieves had run away. 　 c. 表示意向的动词，如hope, wish, expect, think, intend, mean, suppose等，用过去完成时表示"原本…，未能…" 　　 We had hoped that you would come, but you didn't. 3)　过去完成时的时间状语before, by, until , when, after, once, as soon as。 　 He said that he had learned some English before. 　 By the time he was twelve, Edison had began to make a living by himself. 　 Tom was disappointed that most of the guests had left when he arrived at the party. 现在完成时用来表示之前已发生或完成的动作或状　态，其结果的确和现在有联系。动作或状态发生在过去　但它的影响现在还存在；也可表示持续到现在的动作或　状态。其构成： have (has) +过去分词。

1.一般过去时表示的是 (1)过去发生的动作 i had lunch yesterday.我昨天吃过午饭. (2)过去的状态 i was ten in 1990.1990年我十岁. 2.现在完成时表示的是 (1)动作发生在过去,现在刚刚完成. i have jast had lunch.我刚刚吃过午饭. (2)动作发生在过去,对现在有影响. i have already had lunch.我吃过午饭了.(意思是我不饿了) (3)动作发生在过去,到现在还没结束. he has lived here for 20 years.他住在这里已经20年了. 3.过去完成时是指动作发生在过去的过去. before he came back,i had already finished the work.他回来之前,我已经完成了工作.("before he came back"是过去的事情," i had alreday finished the work"发生在这之前,所以叫过去的过去.