More and more people around the world are learning Chinese now.=more and more people _ _ the
world are learning Chinese now.
They must go to bed before 10:00 p.m.=_ is _ _ _ _ _ go to bed before 10:00 p.m.
It's not a good idea to keep a big dog in a small flat.=We _ keep a big dog in a small flat.
She must finish her work before playing with her cat.(否定句）she _ _ _ finish her work before _ _ with her cat.