现在完成时是英语中一个很重要的时态，也是很容易弄错的一个时态。归纳起来，现在完成时共有四种主要用法，现分别解说如下：
一、现在完成时表示影响
该用法的现在完成时表示一个过去发生的动作在过去已经完成，并且这个过去发生并完成的动作对现在有影响或结果，同时说话者强调的或感兴趣的就是这个影响或结果，如汉语说“他已离开这个城市了”，其中的“离开”肯定发生了，它对现在的影响或结果就是“他现在已不在这个城市了”；又如汉语说“有人把窗户打破了”，显然“打破窗户”这一动作发生在过去，并且在过去已经完成了，但说话人强调的重点是打破窗户对现在的影响——窗户现在仍是破的。如：
He has left the city. 他已离开这个城市。(结果：他不在这个城市。)
Someone has broken the window. 有人把窗户打破了。(结果：窗户仍破着。)
I have lost my pen. 我把钢笔丢了。(结果：我现在无钢笔用。)
He has finished his work. 他把工作做完了。（结果：他现在可以做其他的事了。）
二、现在完成时表示持续
该用法的现在完成时表示一个过去发生的动作或开始的状语在过去并未完成或结束，而是一直持续到现在，并且有可能继续下去(也可能到此结束)，如汉语说“他在我们学校教书已有30年了”，显然“他在我们学校教书”是从30年前开始，并且一直教到现在，已经持续了30年；又如汉语说“自上个星期以来他一直很忙”，显然“忙”是从上个星期开始的，并且这一“忙”就一直忙到现在。如：
He has taught in our school for 30 years. 他在我们学校教书已有30年了。
He has been busy since last week. 自上个星期以来他一直很忙。
He has worked for us ever since he left school. 他离开学校以后就一直为我们工作。
三、现在完成时表示重复
即表示从过去某个时间直到现在的这个时间范围内不断重复发生的动作或情况，并且这个不断重复的动作有可能继续下去，也有可能到现在就结束。如：
How often have you seen her? 你隔多少见她一次?
My father has always gone to work by bike. 我父亲一向骑车上班。
四、现在完成时表示将来
同一般现在时可以表示将来一样，现在完成时也可以在时间状语从句里表示将来。如：
I’ll wait until he has written his letter. 我愿等到他把信写完。
When you have rested, I’ll show you the garden. 等你休息好之后，我领你看我们的花园。
【跟踪训练】
1. We _______ to move but are still considering where to go to.
A. are deciding B. decided C. have decided D. had decided
2. I left my pen on the desk and now it’s gone; who _______ it?
A. took B. has taken C. will take D. had taken
3. I feel sure I _______ her somewhere before.
A. was to meet B. have met C. had met D. would meet
4. —Will you go to the park now?
—Not until I _______ my physics exercises.
A. will finish B. have finished C. will have finished D. had finished
5. —Did you enjoy the film?
—Yes, it’s the best one I _______ these years.
A. had B. have had C. had had D. would have
6. —Why do you look worried?
—Fred left the company half an hour ago. His work _______ unfinished since.
A. left B. was left C. has left D. has been left
7. —Why did you come by bus?
—My car broke down yesterday evening and I _______ it repaired.
A. didn’t have B. don’ t have C. won’t have D. haven’t had
8. There _______ less accidents on this road since the speed limit was introduced.
A. have been B. were C. had been D. have had
9. Look at that little boy wandering about—perhaps he _______ his mother.
A. will lose B. is losing C. had lost D. has lost
10. The plans _______ under discussion for a year now, but no decision _______ reached.
A. have been, has been B. are, is
C. have been, is D. are, has been
11. —I suppose you ______ that report yet?
—I finished it yesterday, as a matter of fact.
A. didn’t finish B. haven’t finished C. hadn’t finished D. wasn’t finishing
12. —_______ any replies yet?
—Six yeses and two noes so far.
A. Do you have B. Did you have C. Have you had D. Had you had
13. — _______ leave at the end of this month.
— I don’t think you should do that until _______ another job.
A. I’m going to; you’d found B. I’m going to; you’ve found
C. I’ll; you’ll find D. I’ll; you’d find
【答案与解析】
1. C。用现在完成时表示影响，即指现在已经作出决定。
2. B。用现在完成时表示影响或结果，即现在笔不见了，结果是由于某人已经把它拿走了。
3. B。before 用作副词时不与具体时间连用，泛指“以前”，通常与一般过去时或现在完成时连用。
4. B。因为在时间状语从句中要用一般现在时代替一般将来时。若强调从句动作发生在主句动作之前时，用现在完成时代替将来完成时，本题属后一种情况。
5. B。因为 these years 是包括现在在内的，故用现在完成时。
6. D。受前一句left的影响，易误选B。题干中的since说明此处应用现在完成时态。从问句中也可看出来，此处强调动作对现在的影响，故要用现在完成时的被动式。
7. D。从昨天坏了一直到今天此时还没有修好，表示从过去某一时刻开始一直延缓到现在的动作或状态要用现在完成时态。
8. A。根据句中的since可知，空格处应用现在完成时。句意为：自从实施速度限制，这条路上的交通事故已经少些了。
9. D。根据前文语境可知，这个小男孩当时在wandering about(慢无目的地闲逛)，所以他有可能已经与他母亲走散了，故用现在完成时最合适。
10. A。根据句中的for a year now可知，计划的讨论到现在已持续了一年，它表示的是从过去一直持续到现在的情况，所以第一空要用现在完成时；而第二空用现在完成时，则表示的是一种结果。
11. B。根据答语的意思“事实上，我昨天就完成了”可知，问话人的意思肯定是“我想你还没有写完报告吧”，所以用现在完成时，表示现在的结果。
12. C。此处用现在完成时表示询问结果。
13. B。从对话内容上看，这是两个关系比较要好的朋友（或熟人或亲人等）之间的谈话。第一空用be going to结构，表示说话者的“打算”；第二空用现在完成时，表示对方的劝告——要等已经找好新的工作，然后再辞职。
引用地址: http://www.yygrammar.com/Article/201112/2725_2.html
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