文档介绍：一、时态讲解：现在完成时
（1）构成：现在完成时由助动词have + 过去分词构成，助动词have 有人称和数的变化。第三人称单数用has，其余用have.
现在完成时的否定式直接在助动词后面加上not、疑问式是把助动词提到主语之前。以study 为例，其否定式、疑问式和简单回答形式如下：
否定式
疑问式
I have not (haven’t) studied….
Have I studied…?
You have not (haven’t) studied….
Have you studied…?
He has not (hasn’t) studied….
Has he studied…?
否定疑问式
简单回答（肯定/否定）
Have I not (Haven’t I) studied…?
Yes, you have. No, you haven’t.
Have you not (Haven’t you) studied…?
Yes, I have. No, I haven’t.
Has he not (Hasn’t he) studied…?
Yes, he has. No, he hasn’t.
（2）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，往往和包括现在在内的表示一段时间的状语连用，如recently, already, just, lately, 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.
★注意：
since和for的区别
since后接时间点，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
2）have