重点3 until 引导的时间状语从句
…until….“直到……时候”；not…until…“直到……才……”
例句：
You are to stay until/till your mother comes back.
The meeting was put off until ten o’clock.
The villagers didn’t realize how serious the pollution was until all the fish died in the river.
→Not until all the fish died in the river did the villagers realize how serious the pollution was.
He didn’t go to bed until his mother came back.
→It was not until his mother came back that he went to bed.（强调句）
Not until he failed in the exam did he realize that he had wasted much time playing computer games.
Not until his son came back from school did he go to bed.
