学习必备欢迎下载时态讲解：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：1）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 t...
