一．Since作为介词，后接某一确定的时间点，主句谓语动词是持续性动词，常与现在完成时态、现在完成进行时态或过去完成时态连用。例如：
1、He left the village in 1982 and I haven’t seen him since then.1982年他离开这个村子，从那以后我再没见过他。
2、She’s been working in a bank since leaving school.她中学毕业后就一直在一家银行工作。
3.He had spoken to her only once since the party. 自从那次聚会以来，他只跟她说过一次话。
二．Since作为副词，表示从过去以来、以后或到现在的情形或状态，常与现在完成时态连用。例如：
1．He left home two weeks ago and we haven’t heard from him since. 他两周前离开了家，到现在我们一直没有他的消息。
2．He came to Zhenjiang 6 years ago and has lived here (ever) since.他6年前来到镇江，从此便住在这里。
三．since引导原因状语从句
作为连词，since可引导原因状语从句，表示因为；既然；鉴于：例如：
1．He didn’t come since he was busy.他因为忙，所以没有来。
2．Since this method doesn’t work,let’s try anoter.既然这种方法不行，我们就试用另一种吧。
四．Since在特殊句型中的应用
句型I：“It is（has been）+时间+since+持续性动词的过去时”，表示“自从……以来到现在已有多久。”例如：
It has been quite some time since I was last in London.我上次离开伦敦至今颇有一段时间了。
句型II：“It was+时间+since+持续性动词的过去完成时”,表示“从……到过去某时间点以来”，例如：It was three years since we had been here.那时我们在这已呆了三年。
六．巩固练习
（一）单项选择
1．—Do you smoke？
—_____ ．It's two years since I smoked．
A．Yes，I do B．No，I don't C．Not too much D．Oh，but I wish I didn't
2．Since you are busy, you __________ tomorrow.
A. don’t need come
B.need not come
C. needn’t come
D.mustn’t come
3.---Has he been home?
---______,he _________home since he graduated.
A. No; hasn't been
B.Yes;has been
C.No; isn’t
D.Yes; is
4．They _________friends since they met in Shanghai.
A.haven’t been
B.have been
C. aren’t
D. a re
5.I_______here since he left the door open,but it seems that he won’t come back today.
A. have been waiting
B.will have waited
C.was waiting
D.waited
6.I _________ from him since he has lived here.
A. heard
B. have heard
C. have never heard
D.have been hearing
7. He came to China _______ 1998.
A. from
B. since
C. at
D. in
8.-- Excuse me.Did you notice whether the No.18 bus had gone by?
--I don't know_ I began to stand here just now.
A.as
B.when
C.since
D.while
现在完成进行时和现在完成时练习
1. —I’m sure Andrew will win the first prize in the final.
— I think so. He ________ for it for months. (2008江苏)
A. is preparing
B. was preparing
C. had been preparing
D. has been preparing
2. By the time he realizes he _________ into a trap, it’ll be too late for him to do anything about it. (2008山东)
A. walks
B. walked
C. has walked
D. had walked
3. So far this year we _______ a fall in house prices by between 5 and 10 percent. (2008福建)
A. saw
B. see
C. had seen
D. have seen
4. Cathy is taking notes of the grammatical rules in class at Sunshine School, where she ______ English for a year. (2007湖南)
A. studies
B. studied
C. is studying
D. has been studying
5. Danny _________ hard for long to realize his dream and now he is popular. (2007福建)
A. works
B. is working
C. has worked
D. had worked ＢＣＡＢＡＣＤＣDCDDC
