在完成时中，一个瞬间性动词（一次性动作如buy, borrow, die, leave, begin, join等）不能与表示一段时间的时间状语（如for, since, how long等）连用，此时须将该瞬间动词改为延续性动词或状态动词。
1 die（表动作）-------------be dead（表状态）
His father died/passed away two years ago.
他的父亲两年前去世。
----------His father has been dead for two years. 或His father has been dead since two years ago.
他的父亲去世两年了。
注：死的动作只是一瞬间就完成了，不可能一直在死；死之后的死亡的状态才可以持续。
2 become------------be
He became a teacher in 1998.
他在1998年成为一名教师。
-----------He has been a teacher since 1998.
自从1998年以来，他就是一名教师。
3 begin/start----------be on
The film began/started ten minutes ago.
电影10分钟前开始放映了。
----------The film has been on for ten minutes.
电影已经放映10分钟了。
4 leave------------be away, leave sp----------be away from sp
Tom left Shanghai a month ago.
汤姆一个月前离开了上海。
------------Tom has been away from Shanghai for a month.
汤姆离开上海已经一个月了。
5 fall asleep------------be asleep
The little baby fell asleep half an hour ago.
那个小婴儿半小时前睡着了。
------------The little baby has been asleep for half an hour.
那个小婴儿已经睡着半小时了。
6 stop/end/finish--------------be over
The film ended an hour ago.
电影半小时前结束了。
-----------The film has been over since an hour ago.
电影已经结束半小时了。
7 put on-------------wear, have on, be dressed in
Jack put on a coat three hours ago.
三小时前杰克穿了一件外套。
---------Jack has been wearing a coat for three hours.
杰克穿上外套已经三小时了。
8 borrow/lend-------------keep
Xiao Ming borrowed a book from the library last week.
小明上周从图书馆借了一本书。（借书的动作瞬间完成，不可能一直在借。）
--------Xiao Ming has kept the book for a week/since a week ago.
那本书小明已经借了一周了。（这里的“借”实际上为保管、持有，所以用延续性动词keep.）
9 buy-------------have
The Zhangs bought their new house three months ago.
张先生一家在三个月前买了他们的新房子。
----------The Zhangs has had their new house for three months.
张先生一家买新房子已经三个月了。（这里的“买”实际上为拥有，所以用延续性动词have.）
10 go back/come back/return----------be back
Li Ming came back from the US three weeks ago.
李明三周前从美国回来了。
-----------Li Ming has been back from the US for three weeks.
李明从美国回来已经三周了。
