条件状语从句

连接词主要有： 如果if、 除非, 如果不unless、只要as/so long as,、如果 on condition that 等。.

unless = if not考试重点.

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 don't leave immediately, or you will be late.　B、D句意不对，or表转折.