條件狀語從句

　　連接詞主要有 if, unless, as/so long as, on condition that 等。.

　　if 引導的條件句有真實條件句和非真實條件句兩種。非真實條件句已在虛擬語氣中闡述。

　　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.

　　典型例題

　　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，否則你就回遲到的�？赊D化為 If you dong leave immediately, you will be late.　B、D句意不對，or表轉折，句子如為 You leave immediately or you will be late.

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