I would like to go to the buddy and tell him not to do so saying that " I know that you know many things buddy. But Every student is not of the same level. Other people are also studying here just to know/understand the things well but if you do not let others participate in the class, they would be left behind. Its' good that you actively participate in class but at the same time, you should also let other participate as well so that your classmates wont' be left behind and they may also understand the concepts. I hope that you are understanding what i am trying to say. Kindly let others participate as well. Thanks ! "

I hope it helps you ! If you dont' mind, can u mark it as the brainlist answer... ;) and dont' forget to say thanks !
First of all I can get him understand that if he doesn't allow anyone to know the studies going in the class then he is just wasting his own time .in future he is going to bear the loss and a good student is always a good listener. he will find this way or the other to be attentive in the class .