时间状语从句 主局用什么时态 从句用什么时态

时间状语从句:
连接时间状语从句的连接词有:
(1) 连词：when,while,as.它们都表示当…时候的意思.如果主句和从句的动作同时发生且都是进行时
态,只用while,as.其他情况下when,while,as通用.
1 When he came in,I was listening to the radio．
2 As I was wandering in the street,I met her.
3 While (as) I was watching TV,my mum was cooking in the kitchen.
(2) 连词before,after,since,until(till).当他们表示时间时,他们既是介词又是连词.
{ He usually drinks a cup of tea before he goes to school.
连词
He usually drinks a cup of tea before going to school.
介词
{
He usually drinks a cup of coffee after he comes back from school.
连词
He usually drinks a cup of coffee after coming back from school.
介词
{
I have lived in Dalian since my son was born in 1999.
连词
通常情况下,主句用现在完成时,从句用一般过去时.
I have lived in Dalian since 1999.
介词
{
I will wait here until(till) you finish your job.
连词
I will wait here until(till) 8pm.
介词
(3) 词组：as soon as
{ I will tell him as soon as he comes back.
As soon as she finishes her homework,she will play tennis.
通常情况下,主句用一般将来时,as soon as 引导的从句用一般现在时.