1. 用方框内所给的词填空。

when    before    while    until    since

1. （1） Mum was making cookies in the kitchen the telephone rang.
3. （2） I was watching TV my wife was cooking.
5. （3） He had worked in a factory for two years he went to college.
7. （4） Four years has passed he married.
9. （5） He didn't get to the airport it was dark.