1、时间状语从句
A． when, while, as, whenever;
when, while, as表示主句谓语作和从句的谓语动作同时发生或几乎同时发生;
海口市面积1．when
①when表示点时间时,从句中用短暂性动词；表示段时间时,用持续性动词;
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When I got home, my family were already having dinner.我到家的时候,全家已在吃晚饭;
when表示点时间
When they were still talking and laughing, the teacher came in. 当他们还在说笑的时候,老师进来了;when表示段时间
He waved hello when he saw her. 当他看见她的时候,就挥手打了个招呼;when表示点时间
When you think you know nothing, you begin to know something.当你认为自己一无所知的
时候,就开始知道一些事情了;when表示段时间
注意当when意思是正当……时候and at that moment时,when只能跟在前一分句之后;
He was about to go to bed when the doorbel rang. 他正要上床,忽然门铃响了;
They were watching the World Cup when suddenly the lights went out. 他们正看着世界杯比赛,突然灯灭了;
They had just arrived home when it began to rain. 他们刚到家,天就开始下雨了;
②有时when表示虽然,尽管的含义,相当于although或since;
He walks when he might take a taxi. 尽管可以打的,但他还是步行;
How can you hope for mercy yourlf when you show none 既然你不宽恕别人,你自己又怎能希望得到别人的宽恕呢
2．while
①while通常表示一段时间,从句中宜用持续性动词作谓语;
Strike while the iron is hot.趁热打铁;
She fell asleep while she was reading the newspaper. 她在看报的时候睡着了;
②while有时可以作并列连词,表示对比,可译成……而……;
I am fond of English while he likes math. 我喜欢英语而他却喜欢数学;
We slept while the captain kept watch. 我们睡觉而上尉担任警戒;
③while有时可引导让步状语从句,意思是虽然;
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While they love the children, they are strict with them. 虽然他们都爱他们的孩子,但却对他们要求严格;
虽然during 与 while 意思很相近,但是during是介词,不能引导从句;
3．as
①as表示点时间时,从句中用短暂性动词；表示段时间时,用持续性动词;as和when两者经常可以通用;
The thief was caught as when he was stealing in the supermarket.小偷在超市行窃时被逮住了;
婴儿湿疹药膏I saw Jim as when he left the meeting room.吉姆离开会议室时候我看到了他;
②as表示 一边……一边……,强调从句和主句中两个动作交替进行或同步进行;
They talked as they walked.他们边走边聊;
He looked behind from time to time as he went. 他一边走,一边不时地往后看;
③as表示随着,此用法不用when或while替代;
As time goes on, it's getting warmer and warmer. 随着时间的推移,天气变得越来越暖了;
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0为什么是偶数As spring warms the earth, al flowers begin to bloom.随着春回大地,百花开始绽放;
4．when, while, as的用法区别
①只有当从句表示的是段时间,即其谓语动词有持续性特征时,这三者可以通用互换;
I got the news on the radio when /while /as I was having breakfast. 我在吃早饭的时候从收音机里获悉这一消息;
②在下列情况下,三者彼此之间不能替换使用：
a．as更强调同一时间或紧接的一前一后或伴随着的变化;
We listened to the singer sing as he played the guitar. 我们听着歌星边弹吉它边演唱;
I thought of it just as you opened your mouth. 你一张嘴我就知道你要说什幺
As he grew older, he became less and less active. 随着他年龄的增长,他变得越来越不活泼了;
提示 状语从句可放在主句之前或之后,放在主句之前时一般用逗号与主句分开;有时可置于主句中间,前后用逗号;
注意as 引导时间状语从句表示“当……的时候”“在……期间”时,该从句的谓语通常是那些表示动作意义的动词,而不能是be是、在, have有,like喜欢,belong属于等表示状态或静态意义的动词;
误I’m going to the post office.—As you are there, can you get me some stamps
正I’m going to the post office.—While you are there, can you get me some stamps
我打算去邮局;——当你在邮局的时候,请帮我买几张邮票好吗
正因为 as 引导时间状语从句表示“当……的时候”“在……期间”时,从句的谓语不能是表示状态或静态意义的动词,所以当下面第一句变为第二句这样的状语从句时,不能再用 as,而应用 when：
As a student he had known great poverty.＝When he was a student he had known great poverty.
他当学生时,经历过很贫困的生活;
b．when更强调特定时间,还可表示从句中的动作先于或后于主句的动作,此时不用as或while;
When I had given Mary the spare ticket, I found my own already gone. 当我把多余的票给了玛丽时,我才发现我自己的票已不知去向;从句动作发生在主句之前,注意主从句的时态
When I finally got there, the meeting had been on for ten minutes. 当我最终赶到那里时,会议已开始十分钟了;从句动作发生在主句之后,注意时态
c．while从句只能表示延续的动作或状态或主从句中动作的对比;
She thought I was talking about her daughter, while in fact, I was talking about my daughter.
她以为我在谈论她女儿,而事实上,我在谈论我的女儿;
d．若表示两个短促动作几乎同时发生时,用as场合多于when;
As he finished his speech, the audience burst into applau. 他结束讲话时,观众爆发出雷
鸣般的掌声;
5．whenever
whenever是when的强势语,它描述的不是一次性动作,而是经常发生的习惯性动作;登录qq空间
You are always welcome whenever you come. 无论你何时来都欢迎;
Whenever we met with difficulties, they came to help us. 每当我们遇上困难的时候,他们就来帮我们;
B． before, after
1．before
before表示在一段时间之前;
I must finish all the work before I go home. 回家之前我必须干完所有的活;
You must first learn to walk before you try to run.在想要跑以前,你得先学会走;
He had learned English for three years before he went to London. 他去伦敦之前已学了三年英语;
She didn’t go out before she finished her homework.她把作业做完才出去的;=not……until……
提示： before 从句往往带有否定的含义,常译为：还没等到….就….；还没来得及…就……趁着还没……就……;作此意时,从句中常见情态动词can/ could;
财务咨询服务He ran off before I could stop him. 我还没来得及阻止他,他就跑掉了;
The man hung up the phone before I could answer it.我没坐多久他就回来了;
He almost knocked me down before he saw me. 他几乎把我撞倒才看到我;
Before I could get in a word, he measured me. 我还来得及插话,他就给我量好了尺寸;
I’ll water the flowers before it gets dark. 我要趁着天还没黑把花浇好水;
Be a pupil before you become a teacher. 先做学生,后做先生;
必背before 常用句型
①It will be + 时间段+before+ 一般现在时：要等多久才…….
It will be five years before we meet again.五年以后我们才能再见;
