单项选择题

The megaphone makes the voice sound louder because it points sound waves in one direction and keeps them from spreading out in all directions.

A．slithering
B．radiating
C．interfering
D．murmuring
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单项选择题
Prohibition in the United States ushered in an era of crime and corruption.
A．introduced
B．caused
C．used
D．upset
单项选择题
Why do you want to throw away those books
A．imitate
B．discuss
C．extract
D．discard
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