1．[2017·湘潭]Sometimes you have to stop ________ too much and just go where your heart takes you.
A．think B．to think C．thinking
2．[2017·益阳]It's necessary for you ________ the classroom clean, class.
A．keep B．keeping C．to keep
3．[2017·邵阳]My little brother didn't go to bed until he finished ________ his homework last night.
A．do B．doing C．to do
