现在完成时两种时间状语
现在完成时属于现在时范围，故不能和表示过去的时间状语连用，如：yesterday, last Sunday,in1990,three years ago 等。它的时间状语有两种情况，下面我们就来区分一下它们。
一、表示结果的副词用作现在完成时的时间状语
1.already和yet。already一般用于肯定句中，yet一般用于否定句和疑问句中。例如：
We have already finished our homework.我们已完成作业了。
2.ever 和never。多用于否定或疑问句中，表示“曾经”或“从未”等。例如：
―Have you ever been to the Great Wall? 你曾经去过长城吗？
―I have never been to the Great Wall.我从未去过长城。
3.用表示到说话为止的过去时间状语，如just, before, up to now, the past/lastfew years等。例如：
I have seen her before, but I can not remember where.
我以前见过她，但记不起在哪里见过。
4.用包括“现在”在内的时间状语，如：now, today, thismorning(month, year, term)等。例如：
―Have you met him today? ―No, I haven’t.
―今天你见过他吗？―我没有。
二、表示动作延续的for，since用作现在完成时的时间状语
现在完成时可以与since或for等表示“一段时间”的状语连用，表示动作或状态从某一时刻开始，一直持续到现在。如：I haven’t seen him for two years. 但是，像come, arrive, buy等终止性动词不能与表示“一段时间”的状语连用。如要用，必须改为“be（在）”等延续性动词来表述。现归纳总结一下由非延续性动词到延续性动词的转换：arrive→ be here，begin(start)→be on，die →be dead，come back→ be back，leave →be away，fall ill(sick，asleep)→ be ill(sick, asleep)，get up→ be up，go out →be out，finish →be over，put on →wear 或be on，open →be open，join →be in或be a member of，close →be closed，go to school→ be a student，borrow →keep，buy→have，catch(a cold)→ have(a cold)，get to know →know，begin to study →study等。例如：He has been a soldier for three years.他参军三年了。begin和start区别
His father has been dead for two years.他父亲去世两年了。
跟踪练习题：
一、用括号中所给动词的适当形式填空。
1. The boy ______ (break) the glass yesterday.
2. After he turned on the light, he ____(begin) to do his homework.
3. We _____ (know) each other since our boyhood.
4.―_____ you _____(see) the English film yet?
―Yes. I _____(see) it last Friday.
5. Mr. Wang _____ (join) the Party in 1999. He _____ (be) a Party member for seven years.
二、单句改错。
1.He has known him since two years.
A    B    C    D
2.The man has left here for two days.
A    B    C    D
3.He has seen the film yet.
A    B    C    D
4.It is five days since the boy has left home.
A    B    C    D
5.The man didn’t the homework.
A    B    C    D
Keys：一、1. broke2. began 3. have known4. Have, seen, saw 5. joined，has been二、1. C since→ for2. C left → been away 3. Dyet → already 4. Dhas left → left 5. Bdidn’
t → didn’t do