keep doing somethingd 用法和理解

keep doing something为连续不断地做某事。有时可以与keep on doing something互换。它们的区别在于keep doing something意为该动作一直不停地在进行中,如：When the train started,she kept waving her hand。而keep on doing something则表示该动作可能停停顿顿但却一直在进行中,如：He kept on making the same mistakes in gramma