keep watch at...keep也不一定加ing?

keep watch at...keep也不一定加ing? keep加ing要双写吗? keep the water boiling为什么这里boiling要加ing keep的动词ing形式 keep keep后面是加do还是加doing,STILL后面是加ING吗? keep staring at keep pets at home watch+ing怎么加? keep at与 keep on与 keep up如何区别 Bill often watch TV at night.watch后面加ing还是es?为什么? You'd better not keep the door open中为什么open不用加ing?