The river will be dirtier and dirtier________we do nothing to protect them．
A．since
B．if
C．unless
D．until
—________
—I have a fever．
A．How are you doing?
B．Are you all right?
C．What’s the matter with you?
D．Do you have a fever?
—Mum，I have a cold．
—You________go to a doctor．I’ll take you to hospital．
A．should
B．shouldn’t
C．need
D．needn't
The doctor advised my father to________smoking．
A．get up
B．stay up
C．put up
D．give up
They are used to________classical music and it makes them feel relaxed．
A．listen
B．listen to
C．listening
D．listening to
When I walked past the playground，I saw many boys________basketball．
A．play
B．played
C．playing
D．are playing
