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 ⋯. Hav e 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 hav Have you not (Haven ’ t you) studied ⋯? Yes, I have. No, I haven
Has he not (Hasn ’ t he) studied ⋯? Yes, he has. No, he hasn
（ 2 ）用法：
） 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 。
She has arrived. 她到了。
）表示持续到现在的动作或状态，往往和包括现在在的表示一段时间的状语连用，
如 recently, already, just, lately, fo r ⋯ , since
ye⋯t
,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：
a) since 和 for 的 区 别
since 后接时间点，如 1993 ， last term, yes terday, 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。
Ex ercise : 用 since 和 for 填 空
Jim has been in Ireland Monday.
Jill has been in Ireland three days.
His aunt has lived in Australia 15 days.
Mary is in her office. She has been there 7 o'clock.
India has been an independent country 1974.
The bus is late. They've been waiting 20 minutes.
Nobody lives in those houses. They have been empty many years.
Mike has been ill a long time. He has been in hospital October.
1. since 2. for 3. for 4. since 5. since 6. for 7. for 8. since
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