1. be doing/ be about to do/ be on the point of doing/ had done..., when... (when: 这时，强调一个动作的突然发生）1) I was walking along the river, when I heard a drowning boy cry for help.2) I was about to leave when it began to rain.3) I had just finished my test paper when the bell rang, announcing the exam was over.2. It was (not) +时间段 +before +一般过去时 "过了一段时间就……"It will (not) be +时间段 +before +一般现在时 "要过一段时间才会……"It is/ has been +时间段 +since...It was +点时间 +when...It was +时间状语 +that... (强调句)1) It was not long before he sensed the danger of the position. 不久他就意识到他处境危险。(动作已发生)2) It will be half a year before you graduate from the school. 还有半年你才从这个学校毕业。(动作未发生)3) It is 3 years since he worked here. = he left here.(since 从句中的谓语动词若是延续性动词，要从这个动作结束的时候算起)4) It was 3 o'clock when they received the telephone.5) It was at 3 o'clock that they received the telephone.3. once... 一旦……，表示时间和条件1) Once you start, you will never give up.2) Once you understand what the teacher explained, you will have no difficulty doing the work.4. the +比较级……，the +比较级…… "越……越……"The more books you read, the more knowledge you will get.5. whether... or... 无论是……还是……1) Whether the weather is good or bad, they will set off as they planned.2) Any person, whether young or old, has his own worth.6. 祈使句 +or/otherwise +结果句或祈使句 +and +结果句1) Stop doing such a foolish thing, or you will be punished in time.2) More effort, and the problem would have been settled.7. every time/ each time/ next time/ the first time/ any time 等短语引导时间状语从句，表示"每当，每次，下次，第一次，任何时候"。1) Every time you meet...
