kept后面加什么形式

　　We kept up a correspondence for many years.

　　我们保持了很多年的通信联系。

　　Have you kept in contact with any of your friends from college?

　　你和你大学里的朋友还保持联系吗？

　　Your application will be kept on file.

　　你的`申请书将存档。

　　The thought kept going round and round in her head.

　　这个想法一直萦绕在她的心头。

　　He kept us at it all day.

　　他让我们不停地干了一天。