硝基外用磁漆干嘛用:The girl fell asleep ______ doing her english exercises. 谢谢

while更强调是正在做的事,注意doing

这问题经常有人问呢.看看它们的区别就行啦.

When和While的区别

①when是at or during the time that, 既指时间点，也可指一段时间，while是during the time that，只指一段时间，因此when引导的时间状语从句中的动词可以是终止性动词，也可以是延续性动词，而while从句中的动词必须是延续性动词。

②when 说明从句的动作和主句的动作可以是同时，也可以是先后发生；while 则强调主句的动作在从句动作的发生的过程中或主从句两个动作同时发生。

③由when引导的时间状语从句，主句用过去进行时，从句应用一般过去时；如果从句和主句的动作同时发生，两句都用过去进行时的时候，多用while引导，如：

a. When the teacher came in, we were talking.

当此句改变主从句的位置时，则为：

While we were talking, the teacher came in.

b. They were singing while we were dancing.

④when和while 还可作并列连词。when表示“在那时”；while表示“而，却”，表对照关系。如：

a. The children were running to move the bag of rice when they heard the sound of a motor bike.

孩子们正要跑过去搬开那袋米，这时他们听到了摩托车的声音。

b. He is strong while his brother is weak.

他长得很结实，而他弟弟却很瘦弱。

while + v+ing

while与when以及as之间的区别。

1. 当从句中的谓语动词是持续性的动作时,我们可以用while, when或as。

While / When / As I was walking down the street, I noticed a police car in front of the bank.我顺着马路往前走时,发现银行门前停着一辆警车。

2. 当从句中的谓语动词表示瞬间动作时,不可用while。

He was on the point of leaving when someone knocked at the door. 他正要走,这时有人敲门。

3. 如果谈论两个长动作,最常用的是while。

While John was sitting biting his nails, I was working out a plan to get us home. 约翰坐在那里咬指甲时,我想出了一个回家的办法。

不过, as是可以用来说明两种正在发展或变化的情况的,这时as引导一个持续性的动作,主句中的动作与之同时进行。

As we talked on, he got more and more excited. 我们继续往下谈的时候,他越来越兴奋。

4. 如果表示两个短动作或事件同时发生,最常用的是as或just as,也可用when。

Just as he caught the ball, there was a tearing sound. 当他抓住球的时候,有一种撕裂的声音。

I thought of it just when you opened your mouth. 就在你要说话的时候,我也想到了。

A