练习题:       1.It's a long time since we ____ (meet) last,isn't it?

3.have got,has got 虽然是现在完成时,但have got=have has got==has

2.when 引导 的特殊问句不与现在完成时连用.

  6. It is /has been +一段时间 + since 从句.自从某事发生已有一段时间了.  eg. It is /has been two years since my brother joined the army. 注意:1.since 引导的从句中动词用过去时

5.现在完成时中的 for 与 since

for + 时间段 与延续性动词的现在完成时连用       since + 时间点/从句

I have kept the library book for a week.= I have kept the library book since a week ago.              

4.现在完成时和一般过去时的区别

现在完成时所表明的是过去发生的动作对现在的影响,强调的是现在的情况,不可以和表示过去的时间状语yesterday,in 1991,three days ago last time,last night等连用一般过去时表明的是过去发生的事实,和现在不发生关系.             

3.现在完成时中been to,gone to和been in/at been to去过某地,表示某人的一种经历,可以和once,twice,already,ever,never等连用.    eg. She has been to Shanghai twice. (表示目前人在这里)               

gone to 去某地了,说话时某人已离开此地,在去某地的途中或已在某地,

eg. She has gone to Shanghai。 (表示现在她人不在这里)               

been in/at 逗留在某地(已经一段时间).常和for ten days,since I came here等连用.

eg. She has been in Shanghai since she moved there.                 

2.初中英语课本中常见终止性动词有:leave, go, come, arrive, begin, buy, borrow, die, join, become等.终止性动词要表示持续时, 可用以下方法:                

⑴.将时间状语改为时间段 + ago,句中谓语动词用一般过去时.

eg.我弟弟参军两年了. My brother joined the army two years ago.               

⑵.若保留for+时间段,since+时间点/从句, 或用在 how long 句型中,则需将终止性动词改为相应的状态动词或延续性动词                      

常见终止性动词与延续性动词(或状态动词)的对应关系如下

come/go/arrive/get/reach/move------be in/at open-----be open

die------be dead close----be closed become---be borrow---keep   begin/start-----be on put on----wear

leave-----be away (from) buy-----have fall asleep----be asleep

end/finish-----be over catch a cold-----have a cold

join the army----be in the army be a soldier     join the Party----be in the Party be a Party member

→My brother has been in the army for two years.   →My brother has been a soldier for two years.

  解析：  1.英语动词根据词义可分为两种,一种是延续性的,一种是终止性的,终止性动词(也可称为非延续性动词,瞬间动词,或点动词),如begin,start,die,buy,leave, come等,表示动作的发生与结束于一瞬间完成,不能再延续,所以它的现在完成时不能和表示延续的时间状语连用,即不能与表示一段时间的状语,for+时间段, since+时间点/从句连用,也不能用在how long引导的特殊疑问句中.

 eg. I've left Shanghai for three days.(×)    I've been away from Shanghai for three days.( √ ).

I left Shanghai three days ago. ( √ )     It is /has been three days since I left Shanghai.( √ )  

2.表示过去发生的动作或存在的状态,一直持续到现在,也许还将继续下去,可以和表示从过去某一时刻延续到现在的一段时间的状语连用,即for +时间段,since+时间点/从句, in the last ten years等,谓语只可用延续性动词.