when引导的时间状语从句

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when引导的时间状语从句，不得不提起as和while
一、whe n可以和延续性动词连用，也可以和短暂性动词连用；而while和as只能和延续性
动词连用。
① Why do you want a new job when youve got such a good one already？（get为短暂性动词）你
已经找到如此好的工作，为何还想再找新的？
②Sorry，I was out when you called me．（call为短暂性动词）对不起，你打电话时我刚好外
出了。
③Strike while the iron is hot．（is为延续性动词，表示一种持续的状态）趁热打铁。
④ The students took notes as they listened．（listen为延续性动词）学生们边听课边做笔记。
二、when从句的谓 语动词可以在主句谓语动作之前、之后或同时发生；while和as从句的谓
语动作必须是和主句谓语 动作同时发生。
1．从句动作在主句动作前发生，只用 when。
①When he had finished his homework，he took a short rest．（finished先发生）当他完成作业
后，他休息了一会儿。
②When I got to the airport，the guests had left．（got to后发生）当我赶到飞机场时，客人们
已经离开了。
2．从句动作和主句动作同时发生， 且从句动作为延续性动词时，when，while，as都可使用。
①When ／While ／As we were dancing，a stranger came in．（dance为延续性动词）当我们跳
舞时，一位陌生人走了进来。
②When ／While ／As she was making a phonecall，I was writing a letter．（make为延续性动词）
当她在打电话时，我正在写信。 < br>3．当主句、从句动作同时进行，从句动作的时间概念淡化，而主要表示主句动作发生的背
景或条 件时，只能用 as。这时，as常表示“随着……”；“一边……，一边……”之意。
① As the time went on，the weather got worse．（as表示“随着……”之意）
② The atmosphere gets thinner and thinner as the height increases．随着高度的增加，大气越来
越稀薄。
③As years go by，China is getting stronger and richer．随着时间一年一年过去，中国变得越来
越富强了。
④The little girls sang as they went．小姑娘们一边走，一边唱。
⑤The sad mother sat on the roadside，shouting as she was crying．伤心的妈妈坐在路边，边哭边
叫。
4．在将来时从句中，常用when，且从句须用一般时代替将来时。
①You shall borrow the book when I have finished reading it．在我读完这本书后，你可以借阅。
②When the manager comes here for a visit next week，Ill talk with him about this．下周，经理来
这参观时，我会和他谈谈此事。
三、when用于表示“一……就……”的句型中（指过去的事情）。
sb．had hardly（＝scarcely） done sth．when．．．＝Hardly ／ Scarcely had sb．done sth．when．．．
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①I had hardly ／scarcely closed my eyes when someone knocked at the door．＝Hardly ／
Scarcely had I closed my eyes when someone knocked at the door．我刚一闭上眼，就有人在敲门
了。
②I had hardly ／scarcely entered my room when the telephone rang．＝Hardly ／
Scarcely had I entered my room when the telephone rang．我刚一走进房门，电话就
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