单项选择题

Air cannot ______,but it is all around us.

A．is seen
B．see
C．be seen
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单项选择题
Be quiet! Someone ______ the piano in the next room.
A．is playing
B．played
C．plays
单项选择题
Can this camera(摄像机) ______ good photos
A．take
B．make
C．pick
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