when, while和as的用法
一．when，while，as在时间状语从句中的区别：
①三者均可表示“当……的时候”，如果主句表示的是短暂的动作，而从句表示的是一段时间，三者可通用。如：
I met Kang Li as／when／while I was walking along the street．当我沿街散步时碰见了康丽。
②when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。 如：
It was snowing when we got to the airport．当我们到达机场时，天正下着雪。（不能用while）
③as强调主句与从句表示的动作同时发生，as常表示“随着……”；“一边……，一边……；while强调主句表示的动作持续于while所指的整个时间内；when可指主、从句所述动作同时或先后发生。如：
As the time went on，the weather got worse．（as表示“随着……”之意）
He sang as he went along．他边走边唱。
Please write while I read．我读的时候，请写下来。
When he reached home，he had a little rest．回到家后，他休息了一会儿。
④when用于表示“一……就……”的句型中（指过去的事情）。
somebody had hardly（＝scarcely） done …when．．．＝Hardly ／ Scarcely had somebody
done …when．．．
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。 二.when, while和as都可引导让步状语从句：
①．when引导让步状语从句，意为“尽管，虽然”相当于though或although:
They stopped trying when they might have succeeded next time. ②while引导让步状语从句，相当于although ，是较为正式的书面语: While I am willing to go, I would like it better that you went. ③as引导让步状语从句必须倒装，从句中的表语，状语或动词原形置于句首，
若表语为名词，前置时省略冠词。 Child as he is, he knows a lot.
Much as I like it, I will not buy it, for it’s too expensive.
Try as he might, he couldn’t find a job.
三.when和while可用作并列连词:
①when作并列连词，意为“突然，正在那个时候”常运用于以下句型中：
Somebody be about to do?when?
Somebody be on the point of doing?when?Somebody be doing? when?
Somebody had done?when?
We were having a meeting when someone broke in.
We were about to set off on our way, when it suddenly began to rain.
②作并列连词，意为“而，却”，表示对比。 He likes pop music, while I am fond of music.
四.when和as用于原因状语从句中:
①when=since, now that? “既然”
Why do you want a new job when you’ve got such a good one already?
②意为“因为”，指说话双方都知道的原因。
As he was not ready in time, we went without him.
组题练习：
1. Success came ______ she began to play leading parts in radio plays.
A. While B. as C. when D. if
2. The atmosphere gets thinner and thinner _______ the height increases.
A. When B. as C. while D. since
3. I was just about to go to sleep______ there was a loud knock on the door.
A. While B. when C. as D. since
4. They were surprised that a child should work out the problem_____ they
themselves couldn’t.
A. When B. where C. until D. while
5. We were swimming in the lake______ suddenly the storm started.
A. When B. while C. until D. before
6. I do every single bit of housework______ my husband Bob just does the dishes
now and then. (04高考广西卷)
A. Since B. while C. when D. as
7. _____ I accept that he is not perfect, I do actually like the person.(04高考江苏卷)
A. While B. Since C. Before D. Unless
8. Jasmine was holidaying with her family in a wildlife park_____ she was bitten on
the leg by a lion.(04高考上海卷)
A. When B. while C. since D. once
9. _____modeling business is by no means easy to get into, the good model will
always be in demand.(o4高考浙江卷)
A. While B. Since C. As D. If
10. All gases and most liquids and solids expand ______ heated.
A. as B. while C. before D. when 11. We have only three books______ we need five.
A. as if B. if C. when D. even though
12.How can we explain it to you_____?
A. while you are listening B. unless you will listen
C. as you won’t listen D. when you won’t listen13._______ I had to
work to support my family.
A. When I was a little child B. While I was a little child C. As I was a little child D. Before I was a little child 14._____________, helicopters flew to the burning building. A. While the firefighters were trying to control the fire B. As the firefighters were trying to control the fire C. As soon as the firefighters were trying to control the fire
D. After the firefighters had controlled the fire
15. The husband was looking after the baby__________.
A. after his wife cooked in the kitchen B. as his wife was cooking in the kitchen C. when his wife was cooking in the kitchen D. while his wife was cooking in the kitchen
16. Look at the sun. It is shining._______ it’s sunny, let’s go for a walk.
A. as B. when C. if D. as soon as
17. The sad mother sat on the roadside，shouting_______ she was crying.
A. what B. when C. as D. which
18. Hardly had we entered the room ______ it began to rain.
A. while B. as C. then D. when
19. ___________, he does get annoyed with her sometimes.(04).
A. Although much he likes her B. Much although he likes her
C. As he likes her much D. Much as he likes her 20.______ years go by，China is getting stronger and richer
. A. When B. As C. While D. Since
Keys:1-10CBBDA/BAAAD
11-20CDAAD/ACDDB
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