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考向13 状语从句
考向一 时间状语从句
when/while/as引导的时间状语从句
一、when引导的时间状语从句
1. when引导的时间状语从句，其动词既可以是延续性动作的动词，也可以是瞬间性动作的动词，而且可以表示主句的动作和从句的动作同时发生，或者从句的动作发生在主句的动作之前。
When you apply for a job, you must present your credentials. 当你申请工作时，你必须递交你的有关证件。（同时）
When the students heard the teacher’s footsteps, they all atopped talking. 当学生们听到老师的脚步声时，他们都停止了讲话。（从句动作发生在前）
2. when还可表示just then（正在那时，突然）的意思，此时其所引导的从句只放在主句之后。
be about to do ... when ... 正要去做某事，突然……
be doing ... when ... 正在做某事，突然……
be on the point of doing ... when ... 正在做某事，突然……
We were about to start when it began to rain. 我们正要动身，突然天下起雨来。
The game had hardly/scarcely/barely begun when it started raining. 比赛刚刚开始就下起雨来。
二、while引导的时间状语从句
while表示＂在某一段时间里＂或＂在……期间＂，其所引导的从句的动作是延续性的，并侧重表示和主句的动作同时发生。
When the teacher paraphrased the text in English, the students listened attentively and took notes. 当老师用英语解释课文时，学生们聚精会神地听并做着笔记。
I can learn while I work. 我可以边工作边学习。
三、as引导的时间状语从句
as引导的时间状语从句其动词的动作是延续性的，而且侧重表示主句和从句的动作交替或同时发生，译为＂一边……，一边……＂或＂随着……＂。
We were having breakfast as she was combing her hair. 她梳头时我们在吃早饭。
It will warm up a little bit on Sunday as the cold front passes. 寒流一过，星期日就会有点暖意了。
【典例分析】
1.（2016· 全国新课标卷III·语法填空）Over time, 45 the population grew, people began cutting food into small pieces so it would cook more quickly.
【参考答案】as/when
【答案解析】考查时间状语从句。句意：随着人口的增长，人们开始把食物切成小块，这样可以煮得快一点，这里是时间状语从句，when意为＂当……的时候＂，后跟长动作或短动作，故填as／when。
2. It’s much easier to make friends ________ you have similar interests.
A. unless B. when C. even though D. so that
【参考答案】B
【答案解析】考查状语从句。由句意＂当你们兴趣相投时，交朋友就容易多了＂可知，这里应该用when引导时间状语从句。
before引导的时间状语从句
一、before的常见意思
1. before＂在……之前＂。
I have finished my dissertation before my supervisor went abroad. 在我的导师出国之前，我已完成了我的学位论文。
I’ll be back before you have left. 你离开之前我就会回来。
2. before＂……之后才＂。
It may be many years before we meet again. 可能要过许多年我们才能再见了。
It was three days before he came back. 他三天后才回来。
3. before ＂尚未来得及 ＂
Before she could move, she heard a loud noise, which grew to a terrible roar. 她还没有来得及动弹，就听见有很响的声音，接着就成了可怕的隆隆轰鸣声。
Before they reached the house, a new great wave came, sweeping down trees, and sweeping them down too. 他们还没到屋子，又一个巨浪打来，冲倒了树，也冲倒了他们。
4. before ＂要……先……＂
You should be a pupil before you become a teacher. 要当老师，先作学生。
5. before＂趁……＂
You should do it before it is too late. 趁现在还不算太晚，你应该赶快做它。
二、掌握热点句型用法
1. it was（not）/had done＋一段时间＋before（vt-ed）…＂还要过多久才……（不多久就……了）＂
It was not long before he returned to Beijing. 不久他就回到北京。
It was long before he married Wei Fang. 过了很久他才娶魏芳。
2.it will（not）be＋一段时间＋before（一般式）… ＂还要过多久才……（不多久就……了）＂
It will be long before he goes abroad. 要过很久他才出国。
3.there is +一段时间+to go（=left）＋before（一般式）... ＂在……之前＂
4.long before ＂不久前＂, 用于一般过去时和完成时中；before long = soon/not long after ＂不久后＂，用于一般将来时和一般过去时中。
【典例分析】
1. We need to get to the root of the problem ______________ we can solve it.
A. while B. after
C. before D. as
【参考答案】C
【答案解析】考查时间状语从句的连接词。句意：在我们解决问题之前，我们需要找到问题的根源。A. while当……的时候，而；B. after在……之后；C. before 在……之前；D. as正如。根据句意可知选C。
2. It ________ long before we ________ the result of the experiment.
A. will not be；will know B. is；will know
C. will not be；know D. is；know
【参考答案】C
【答案解析】句意：不会过很长一段时间我们就会知道实验结果。应使用It was not long before的创新句型It will not be long before，before引导时间状语从句时，从句应用一般现在时代替一般将来时。
as soon as/once/directly/the instant等引导的时间状语从句
as soon as 是最常见的表示＂一……就……＂的从属连词，其他连词还有once（一旦），directly（老式英国英语），immediately（主要用于英国英语），instantly，the instant (that)，the minute(that) ，the moment(that)等，它们通常都可与as soon as换用。
As soon as we got home, the telephone rang. 我们一到家，电话就响了。
I recognized her immediately I saw her. 我一看见她就认出她来了。
Directly the teacher came in everyone was quiet. 老师一进来，大家就静了下来。
hardly...when/no sooner...than引导的时间状语从句
hardly/barely/scarcely...when和no sooner...than的意思是＂刚……就＂，它们所引导的从句中的谓语动词通常为过去完成时。
He had no sooner (no sooner had he) arrived home than he was asked to start on another journey. 他刚一到家，就又要他出另一次差。
★ hardly/barely/scarcely和no sooner置于句首时，从句要倒装。
No sooner had the words been spoken than he realized that he should have remained silent. 这些话刚一出口，他就意识到自己应该保持沉默。
since引导的时间状语从句
在含有since引导的时间状语从句的复合句中，从句的谓语动词通常为一般过去时，主句的谓语动词通常为现在完成时。
We’ve never met since we graduated from the college. 大学毕业后我们就再没见过面。
Great changes have taken place since you left. 你走了以后，这里发生了巨大的变化。
【典例分析】
1.（2017·天津卷·完形填空）She had been talking to her mother about the lives of homeless people 42 they first saw the homeless man.
A. since B. unless C. although D. as
【参考答案】A
【答案解析】考查连词。A. since自从；B. unless 除非；C. although尽管；D. as因为。句意：自从他们第一次看到无家可归的人，Hannah就一直在跟她的妈妈说流浪者的生活，根据句意可知选A。
2. I have heard a lot of good things about you I came back from abroad.
A. since B. until C. before D. when
【参考答案】A
【答案解析】考查状语从句。题干中主句谓语动词用现在完成时，从句中谓语动词用一般过去时，由题干意思可知所填词意思是：自从，因此用since引导时间状语从句。句意：自从我从国外回来后，我已经听说了很多关于你的好事。
till/until引导的时间状语从句
till和until同义，作＂直到……时(为止)＂解，till多用于非正式文体，until多用于
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