Our teacher is coming, please stop __________and keep ______

D

stop doing sth.是停止做某事，指停止做原来的事。如： Hearing the doorbell,she stopped washing the dishes. 听见门铃声，她停止洗碗了。 stop to do是停下（手头的事情）去做另外一件事。如：Hearing the dollbell, she stopped to open the door. 听见门铃声，她停下手中的活去开门。本题是说老师来了，当然是指应停止交谈，用stop doing；keep后应接形容词作表语，keep quiet“保持肃静”。故选D。