现在完成时
1.现在完成时的构成：
现在完成时由助动词have\has + 过去分词构成，第三人称单数用has，其余用have。
I have been in Shenzhen for seven years.
Lily hasn’t been to America before.
2.现在完成时的用法：
1）现在完成时通常表示在说话之前已经完成的动作或存在的状态。说话人强调的是该动作或状态对现在的结果或影响。
My daughter has just gone out. 我女儿刚出去。
I’m sure we’ve met before. 我肯定我们以前见过面。
She has arrived. 她到了。
2）表示持续到现在的动作或状态, for…, since…,yet等。如：
I haven’t heard from her these days. 这些日子我没有收到她的信。
We haven’t seen you recently. 最近我们没有见到你。
They have been away for two years. 他们离开已经两年了。
She has been with us since Monday.
3.常和现在完成时连用的时间状语：
already, yet, before, lately, recently, once, twice, ever, never，since，for等连用。例如：
She has already come. 她已经来了。
I haven’t read it yet. 我还没读过这个。
They have never been to Yan’an. 他们从未去过延安。
I haven't seen him lately. 我近来没看到他。
She has been an independent girl since her father passed away.
自从父亲去世后，这女孩就变得独立了。
Jack has been a doctor for 10 years.杰克做医生已经10年了。
4.现在完成时的否定式和疑问句。
否定句：在have\has后加not 结构：主语+has\have+not+过去分词+其他
一般疑问句：Has\Have提到主语前，其他照写。结构：Have\Has+主语+过去分词+其他
特殊疑问句：特殊疑问词+一般疑问句
注意：肯定句中如有some\and，在否定句或者一般疑问句中要变成any\or，即
some-any and-or
以study 为例，其否定式、疑问式和简单回答形式如下：
5.部分不规则变化动词表
6.注意：
和for的区别
since后接过去的某个时间点，如1993，last term, yesterday, the time I got there
for后接一段时间，表示“长达多久”，如ten years, a while, two
days等。
Exercise: 用since和for填空
1. Jim has been in Ireland ______ Monday.
2. Jill has been in Ireland ______ three days.
3. His aunt has lived in Australia ______15 days.
4. Mary is in her office. She has been there ______ 7 o'clock.
5. India has been an independent country ______1974.
6. The bus is late. They've been waiting ______ 20 minutes.
7. Nobody lives in those houses. They have been empty ______
many years.
8. Mike has been ill ______a long time. He has been in
hospital ______ October.
2.表示短暂意义的动词如arrive, leave, borrow, buy, begin, start, die等，在完成时当中不能和表示一段时间的状语连用，因为它们表示的动作不可能持续。因此，不能说：
He has come here for 2 weeks. ×
The old man has died for 4 months. ×
They have left only for 5 minutes. ×
以上三句话可以改为：
He has been here for 2 weeks.
The old man has ______ _______ for 4 months.
They have _____ _____ only for 5 minutes
(has) been（to\in）+地点和have (has) gone(to)+地点的区别：“曾到过某地” =“have (has) been”; 去过，现在已经回来了。“已经去某地”= “have (has) gone”。去了没有回来。
试比较：
Where has he been 他刚才到哪里去了（已经回来了）
Where has he gone 他上哪儿去了（人不在）
They have been to Canada. 他们到过加拿大。（现在已经不在加
