You are to stay here until / till your mother comes back.
The meeting was put off until ten o’clock.
Not until we watched the Earth Day program on TV did we know much about global warning.
= We did not know much about global warning until we watched the Earth Day program.
= It was not until we watched the Earth Day program on TV that we knew much about global warming.
Not until he failed in the exam did he realize that he had wasted much time playing computer games. 【已有很多网友发表了看法，点击参与讨论】【对英语不懂，点击提问】【英语论坛】【返回首页】