第1个回答 2013-05-09
1. “主将从现”原则
即若主句为一般将来时，时间和条件状语从句通常要用一般现在时表示将来，而不能直接使用将来时态。如：
I’ll give her the telex when she comes. 她来时把电传交给她。
I’ll return the book as soon as I have read it. 这书一看完我就送还。
He’ll have four years at university after he leaves school. 他中学毕业后要上四年大学。
2. since与完成时
since 引导时间状语从句时，其主句通常要用现在完成时，有时也用现在完成进行时。如：
She has had another baby since I saw her last. 从上次我见到她以来，她又生了一个孩子。
He has grown an inch since I saw him. 我上次见到他以后他已长高了一英寸。
注：当主句为“It + be + 一段时间”时，则通常用一般现在时代替现在完成时。如：
It’s more than three years now since I saw her last. 我们已有三年多没见面了。
3. 特定句式的时态
由no sooner. . . than, hardly [scarcely]…when引出的时间状语从句，其主句通常用过去完成时，从句通常用一般过去时。如：
Hardly had he arrived when she started complaining. 他刚到她就抱怨起来。
No sooner had he gone to sleep than the telephone rang. 他刚睡着电话铃就响了。
We had no sooner set out than a thunderstorm broke. 我们刚出发就下起一阵雷暴。
No sooner had she agreed to marry him than she started to have terrible doubts. 她刚同意嫁给他她就开始产生可怕的疑虑。
希望能帮助你
第2个回答 2013-05-09
对于WHILE 的时间状语:
while引导时间状语从句，从句中的谓语动词必须是延续性动词。如：be，stay，eat，wait，live等。
(1) 如果主句的动作和从句的动作同时发生，从句常用进行时。如：
While I was crossing the road, I saw him.
我在过马路的时候看见了他。
(2) 如果主句和从句主语相同，且从句谓语中又包含be动词， while引导的从句可用while+ving代替。如：
He was doing his homework while he was listening to music.
He was doing his homework while listening to music. 他边听音乐边做作业。本回答被网友采纳