3）现在完成时可表示持续到现在的动作或状态，动词一般是延续性的，如live, teach, learn, work, study, know.
　 过去时常用的非持续性动词有come, go, leave, start, die, finish, become, get married等。
　举例：
　 I saw this film yesterday.
　　（强调看的动作发生过了。）
　 I have seen this film.
　　（强调对现在的影响，电影的内容已经知道了。）　
　 Why did you get up so early?
　　（强调起床的动作已发生过了。）
　 Who hasn't handed in his paper?　
　　（强调有卷子，可能为不公平竞争。）
　 She has returned from Paris.