是动词词性，例如：
1、I go swimming every day in order to keep fit.我每天游泳以保持健康。
2、You'll need to keep a clear head for your interview.你面试时需要保持清醒的头脑。
3、I said I'd go just to keep him happy.我说过我要去只是为了让他高兴。
4、It is important to keep in touch with the latest research.及时掌握最新研究情况很重要。
