19.6 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.