内容:<br>答:<br>when 与while 用法解析<br>连接词when与while是一对常与过去进行时合作的twins。但正如世界上没有两片完全相同的树叶一样,when与while在有着某些相似之处的同时,彼此也各有一些区别于对方的截然不同的“独特个性”。Do you want to know the differences between them?请看——<br>when 解析版<br>[引导时间状语从句]具体地说,它有以下几种含义:<br>1.表明一个动作发生的时候,另一个动作正在进行之中。例如:<br>When the teacher came into the classroom ,we were reading English.当老师走进教室时,我们正在读英语。<br>2.表明当某一动作正在进行时,另一动作发生了。如:<br>When Kate was flying a kite,she found a wallet lying on the ground.凯特正在放风筝时,她发现地上有个钱包。<br>[特别提示]当when从句放在主句之后时,它更强调某一动作的突然性,此时的when相当于and then,and suddenly,just at that time。如;<br>1.We were watching TV when the telephone rang.(=We were watching TV and suddenly the telephone rang.)我们正在看电视,(突然)电话铃响了。<br>试比较:When we were watching TV, the telephone rang.我们正在看电视时,电话铃响了。<br>2.The boys were playing football when it began to rain.男孩子们正在踢球时,(不料)开始下雨了。<br>3.I was taking a walk when I came across Lily.我正在散步时,(没想到)遇见了莉莉。<br>特别是主句中有just,或when从句中有suddenly时,这种突然性更为明显、强烈。例如:<br>4.He was just falling asleep when he heard someone s
You can go home as soon as your homework has been finished.<br>4. 注意<br>1)现在完成时的被动语态的两个助动词:have/has和been 缺一不可。<br>2)注意与一般过去时被动语态的区别。一般过去时的被动语态表示一个被动的动作发生在过去,其结果对现在没有影响;而现在完成时的被动语态的动作或状态尽管发生在过去,但侧重说明该动作或状态对想在造成的影响或结果。<br>The machine has been repaired.(说明动作发生在过去,对现在有影响,“修好了”)<br>The machine was repaired yesterday.(只说明动作发生在昨天)<br>3)不可与确定的表过去或将来的时间状语连用(如yesterday,three days ago,in 1970,in 2050等),但可与不确定的时间状语连用(如already,yet,just,often,recently,in the past few years等)<br>They have been punished recently.<br>4)有些动词像finish,buy,start,begin,return,join,marry,open,die等,表示的动作很短暂,我们称之为短暂性动词或非延续性动词。它们构成的现在完成时的被动语态不能够与for构成的短语,since构成的短语或引导的句子连用,也不能用于How long…?句型中。