a. since
+具体时间，表示动作或状态从何时开始
Since
then, he has developed another bad habit.
自那以后他养成了另一个坏习惯。
He
hasn't been home since he graduated.
他毕业后就没回过家。
b. for +一段时间，表示动作或状态持续了多久
We have
worked here for ages.
我们在这里工作很久了。
There
has been no rain here for nearly two months.
这里已经近两个月没有下雨了。
c. until
now, up till now, so far, up to the moment
到目前为止
I have
not seen him so far.
到目前为止我没见过他。
Up to
the present, everything has been OK.
到目前为止一切正常。
d.
in/during the past/last five years
在刚刚过去的5年里
He has
been away from school during the last few weeks.
过去的几个星期里他没在学校。
In the
past few years they have dealt with quite a few international corporations
successfully. 在过去的几年中他们已经和好几家跨国公司做成了生意。
e. all
the while, all day一直，一整天
She has
been busy all day.
她忙了一整天。
4．现在完成时和一般过去时的区别
①两者都可表示过去发生过的动作，但前者表示的是过去的动作对现在的影响，而后者则只是表示过去有这一动作的事实。
He
locked the door.
他锁过门。（但现在门是开是锁不清楚。）
He has
locked the door.
他把门锁上了。（现在门是锁着的。）
Who
turned on the light?
谁开的灯？（着眼开灯的动作，不管现在灯是开是关。）
Who has
turned on the light?
谁把灯打开了？（着眼开灯的结果，即现在灯还亮着。）
②两者都可表示过去开始并延续了一段时间的动作，现在完成时表示该动作仍在继续，而一般过去时则说明该动作现已终止。
He has
lived in Beijing for four years.
他在北京住了四年了。（现在仍住那儿）
He lived
in Beijing for four years.
他曾在北京住了四年。（现在不住那儿了）
B．过去完成时
过去完成时的动作须在过去某一时间之前发生，即发生在“过去的过去”。
1．过去完成时的构成
过去完成时是由“had+过去分词”构成的。
Soon I
realized I had made a serious mistake.
我很快就意识到我犯了一个严重的错误。
The man
sitting beside me on the plane was very nervous. He had not flown before.
飞机上坐在我旁边的人很紧张，他以前从没乘过飞机。
Had he
gone home when you arrived?你到的时候他已经回家了吗？
2．过去完成时的用法
①“已完成”用法
表示某一动作或状态在过去某一时间之前或过去某一动作之前已经完成。句中常用by引导的时间状语或以before,
until, when, than等词引导的内含一般过去时的时间状语从句。
By 5:00
yesterday morning we had done that work.
到昨天早上5点钟时，我们已经做完了那件工作。
He had
just finished sweeping the classroom when the teacher returned from the office.
老师从办公室回来时，他刚把教室打扫完。
They
came earlier than we had expected.
他们到得比我们预料的要早。
I had
learnt 5000 words before I entered the university.
我在进大学之前就已学了5000个单词。
It
rained yesterday after it had been dry for many months.
旱了好几个月之后，昨天下雨了。
注意：
在包含before和after的复合句中，因为从句动作和主句动作发生的先后顺序已经非常明确，可以用一般过去时代替过去完成时。
The
train (had) started before I reached the station.
在我到达车站之前，列车已经开了。
After he
(had) arrived in England, Marx worked hard to improve his English.
马克思到达英格兰之后，努力提高他的英语水平。
②“未完成”用法
表示一个动作或状态在过去某一时刻之前就已开始，一直持续到这一过去时间，还可能再持续下去。
Up to
that time all had gone well.
直到那时一切都很顺利。
John and
Jane had known each other for a long time before their marriage.
约翰和简在结婚前就认识很长时间了。
She said
she had made much progress since she came here.
她说自从她到这儿后已取得了很大的进步。
③“想象性”用法
过去完成时有时表示一种未实现的愿望或想法，主要用在if引导的和过去事实相反的条件句以及wish,
as if引导的从句中。
If she
had worked hard, she would have succeeded.
要是她努力的话，她就会成功了。（事实上她没努力，也没成功。）
I wish I
had gone with you to the concert.
我要是和你一起去音乐会就好了。
The two
strangers talked as if they had been good friends for many years.
那两个陌生人交谈起来就像是多年的老朋友。
④表示“刚刚……就……”
过去完成时常用在hardly/scarcely/barely
... when..., no sooner ... than ...等结构中，表示“刚刚……就……”。
Hardly
had he begun to speak when the audience interrupted him.
他刚开始演讲，听众就打断了他。
No
sooner had he arrived than he went away again.
他刚到就又走了。
提示：
intend,
mean, hope, want, plan, suppose, expect, think等动词的过去完成时可以用来表示一个本来打算做而未做的事。
I had
meant to come, but something happened.
我原本打算来的，但有事发生了。
I had
intended to call on you, but was prevented from doing so.
我本打算去看你的，但没能去成。
They had
wanted to help but couldn't get here in time.
他们原想帮忙的，但没能及时赶到这里。
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