you better后面加动词什么形式 betterme是什么意思

后面加动词原型 

例句：

　　1、I think you'd better tell us why you're asking these questions.

　　我想你最好告诉我们你为什么要问这些问题。

　　2、Now that you are here, you'd better stay.

　　既然你已经来了，最好还是住下。

　　3、Maybe you'd better tell me what this is all about

　　也许你应该告诉我这究竟是怎么事。