时间状语从句
2.till, not … until …, until 当时间状语从句在句首时多用until;not…until用于强调句,not和until一并前移,主倒从不倒 3.before, since since:注意区分从句中动词是瞬间还是延续型动词 含有before的常用句型有: It is long before. 过了很久才…… It is not long before. .过了不久就…… It was some time before. .,过了一段时间才…… It will be十一段时间+ before. .多久之后才(就)……