as,when和while的區(qū)別：

　　1、As/When/While：A was happening, B happened或B happened as/when/while A was happening.

　　as,when,while用來表示“當(dāng)某事發(fā)生的時(shí)候，一個(gè)長的行為或事件正在進(jìn)行”。

　　當(dāng)從句引導(dǎo)的句子表示持續(xù)性動(dòng)作時(shí)，as/when/while引導(dǎo)的從句一般用過去進(jìn)行時(shí)（was/were+動(dòng)詞ing）。例如：

　　As I was walking down the street I saw Joe driving a Porsche.當(dāng)我正在沿著街道走的時(shí)候，我看到喬正開著保時(shí)捷。

　　The telephone rang when i was having a bath 當(dāng)我正在洗澡的時(shí)候，電話鈴響了。

　　as，when，while都可以用現(xiàn)在時(shí)態(tài)，如：

　　Please don't interrupt me when I'm speaking.當(dāng)我說話的時(shí)候，請不要打斷

　　I often get good ideas while I'm shaving.當(dāng)我刮胡子的時(shí)候，我經(jīng)常能想到好點(diǎn)子。

　　2、 while A was happening,B was happening或While A happened, B happened

　　while用來表示兩個(gè)長動(dòng)作或事件過去同時(shí)發(fā)生，用過去進(jìn)行時(shí)或者過去時(shí)態(tài)。如：

　　While you were reading the paper ,I was working.當(dāng)你在讀報(bào)紙的時(shí)候，我正在工作。

　　John cooked supper while I watched TV.當(dāng)約翰在煮晚飯的時(shí)候，我在看電視。

　　也可以用現(xiàn)在時(shí)態(tài)，如：

　　After supper,I wash up while Mary puts the children to bed.晚飯后，當(dāng)瑪麗弄孩子們睡覺的時(shí)候我在洗漱。

　　3、As A happened,B happened.

　　B happened,as A happened.