条件状语从句的时态最好具体的说时间状语从句也说一下

条件状语从句
连接词主要有 if,unless,as/so long as,on condition that 等..
if 引导的条件句有真实条件句和非真实条件句两种.非真实条件句已在虚拟语气中阐述.
unless = if not.
Let's go out for a walk unless you are too tired.
If you are not too tied,let's go out for a walk.
典型例题
You will be late ___ you leave immediately.
A.unless B.until C.if D.or
答案A.句意：除非你立即走,否则你就回迟到的.可转化为 If you dong leave immediately,you will be late.B、D句意不对,or表转折,句子如为 You leave immediately or you will be late.
比较while,when,as
1）as,when 引导短暂性动作的动词.
Just as / Just when / When I stopped my car,a man came up to me.
2）当从句的动作发生于主句动作之前,只能用when 引导这个从句,不可用as 或 while.
When you have finished your work,you may have a rest.
3）从句表示"随时间推移"连词能用as,不用when 或while.
As the day went on,the weather got worse.
日子一天天过去,天气越变越坏.