【问】 keep doing sth.与keep on doing sth.在意义上究竟有无区别?
 【答】 对于初学者，只指出keep doing sth.和keep on doing sth.意思一样，就足够了(都表示continue doing sth.)。
 1. He keeps (on) interrupting(=interrupts continually).(LDAE)
 他不停地打断别人讲话。
 2. Why does she keep(on) giggling? (OSD)
 她为什么老是不停地傻笑?
 对于英语水平较高的学习者，则应指出：keep doing sth.常常含有不间断的意思，而keepon doing sth.则可能含有间断的意思，但是更强调“反复”和“决心”，而且常常附加感情色彩：
 1. He keeps on phoning me and I really don't want to talk to him.(PEU)
 他老是不断地给我打电话，而我真不愿意跟他谈话。
 2. Do be quiet，Sally，and don't keep on asking such silly questions.
 安静点，萨莉，别老是问这种愚蠢的问题。
 3. I keep on forgetting to post my wife's letters!
 我总是忘记把我妻子的信件给寄出去!
 4. Why do you keep on smiling? (Mansfield)
 你为什么老是笑?
 5. You keep on making the same mistakes.
 你总是犯同样的错误。
 6. He kept on wiping his eyes with the back of his hand. (Greene)
 他总是用手背擦眼睛。
 7. My friends kept on offering me cigarettes and cigars. (New Concept English，Book 2，
 L.78)
 我的朋友们老是不断地给我递香烟和雪茄。
 8. In the years that followed，Marx kept on studying English and using it.在这之后的几年中，马克思继续学习英语并使用英语。
 请做下面的英语试题：
 1. To keep on doing something is to____.
 A. stop doing it B. refrain from doing it
 C. continue doing it D. avoid doing it (TOEFL教程)
 2. From time to time a wave burst over the boat and swept over him，but he kept____for ten minutes.
 A. to work B. to working
 C. on working D. on work(Nelson，450D)