when-before-since区别及用法课件.ppt

when,before,since句型归纳; 1、when 句型：(1) be doing sth…when… He was still smiling when the door opened and his wife came in.? 他正笑着的时候门突然开了，他妻子走了进来。(2) be about to do sth…when… We were about to start when it began to rain. 我们刚要出发，天就开始下雨了。(3)be on the point of doing…when正要…这时… We were on the ponit of giving up when a truck came into our sight. 我们正要放弃，这时看到了一辆卡车。 ;(4)hardly /sceracely…when…(一…就…) He had /hardly/scarcely fallen asleep when the telephone rang.? 他刚要入睡电话就响了。 (5) had just done …when …(刚做完…某事发生)I had just gone to bed after a very hard day when the phone rang.?在劳累了一天之后我刚刚就寝，电话铃就响了。 (6)还可以表示原因“既然”，相当于since; considering that.  It was foolish of you to take a taxi when you could easily walk there in five minutes .;(4)hardly /sceracely…when…(一…就…) He had not/hardly/scarcely fallen asleep when the telephone rang.? 他刚要入睡电话就响了。 We had scarcely arrived when he asked us to leave. 我们才刚刚到他就叫我们走了.;before sb can/ could … 某人还没来得及……Before I could get in a word ，he had measured me．?我还没来得及插话，他就给我量好了尺寸 It will be/was +时间段+ before 过一段时间才…… ?It will be 4 years before he graduates. 他还有四年时间毕业了。 It was 5 minutes before he left.过5分钟才离开 ??; It won’t be long ……before….（从句用现在时） It wasn't long……before….（从句用过去时） 没过多久/用不了多久……就…… eg:It wasn't long before i found a job. It won't be long before our contry becomes a developed country.我们国家很快就会成为一个发达国家。 before long (adv.)不久，long before 很久以前 ??; (3) had done … before?? （才……）????? We had sailed four days and four nights before we saw land.????????? 我们航行了四天四夜才见到陆地。?? (4)? had not done --- before ---?? 不到……就……????? We hadn’t run a mile before he felt tired.  我们还没走到一英里路他就觉得累了。; It is/has been＋时间段＋since sb. did… §①§did动作为瞬间动词（非延续性），翻译为自从某事发生以来有多长时间 It is 5 years since he left Beijing . 他离开北京5年了 It has been 3 years since he came back from abroad.自从他回国已经三年了 ; It is/has been＋时间段＋since sb. did… §②§did动作为持续动词（延续性），翻译为自从不做