現(xiàn)在完成時
 構(gòu)成:主語 助動詞have, has 過去分詞
用法:
 1) 表示過去發(fā)生的和現(xiàn)在有某種聯(lián)系的動作,常和just, usually, already, since等時間副詞連用。
   I have just had lunch. (飽了,不用再吃了。)
   He has had a cup of tea.(不渴了,不用再喝。)
   They have already had their holiday. (不能再度假了。)
   The boy has already read the book. (已經(jīng)知道書的內(nèi)容了,不用再看了。)
 2) 詢問別人是否做過某事一般用現(xiàn)在完成時:
   Have you finished your homework?
   Have you been to Beijing?
   Has he seen the film?
 3) 表示開始于過去并持續(xù)到現(xiàn)在的動作
   I have lived in Beijing for twenty years.
   I have worked for this school for 1 year.
 4) 表示一種經(jīng)歷,經(jīng)驗:去過…地方,做過…事情,經(jīng)歷過…事情
   I have never had a bath.
   I have never seen a film.
   I have never been to cinema.
   I have ever been to Paris.
   Have been to表示去過,have gone to 表示去了
   I have been to London.(人已經(jīng)回來)
   He has gone to London.(人還在那里)
 5) 表示一種結(jié)果, 一般不和時間副詞聯(lián)用
   I have lost my pen.
   I have hurt myself.
   He has become a teacher.
   She has broken my heart.
 
句型變化:
 ★變疑問句將助動詞移到句首,變否定句在助動詞后面加not.
   Have you lost your pen? I have not lost my pen.
 ★肯定回答及否定回答
   Yes, I have. / No, I have not.
 ★特殊疑問句
   What have you done?
   What has he done?
一般過去時與現(xiàn)在完成時的區(qū)別:
   凡是有明確的表示過去的時間狀語的句子為過去時。
   注意:有些動詞表示的動作有一個終點,不能再延續(xù),因此不能和表示一段時間狀語連用。
   錯:I’ve left Beijing for 3 days.
   對:I left Beijing 3 days ago. I have been away from being for 3 days.