keep后面加什么形式

　　I go swimming every day in order to keep fit.

　　我每天游泳以保持健康。

　　You'll need to keep a clear head for your interview.

　　你面试时需要保持清醒的头脑。

　　I said I'd go just to keep him happy.

　　我说过我要去只是为了让他高兴。

　　It is important to keep in touch with the latest research.

　　及时掌握最新研究情况很重要。

　　Keep going like that ─ you're doing fine.

　　就这样做下去——你做得蛮不错嘛。