現在完成時：構成：主語+助動詞have, has+過去分詞

　　用法：

　　1)表示過去發生的和現在有某種聯系的動作，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. （已經知道書的內容了，不用再看了）

　　2)詢問別人是否做過某事一般用現在完成時：

　　Have you finished your homework?

　　Have you been to Beijing?

　　Have he seen the film?

　　3)表示開始于過去并持續到現在的動作

　　I have lived in Beijing for twenty years.

　　I have worked for this school for 1 year.

　　4)表示一種經歷，經驗：去過…地方，做過…事情，經歷過…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.(人已經回來)

　　He has gone to London.（人還在那里）