单项选择题

Which sound can most people's ears pick up（）

A．Sounds of 15,000 hertz.
B．Sounds of 20,200 hertz.
C．Sounds of 30,000 hertz.
D．Sounds of 50,000 hertz.

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单项选择题What is most noise pollution damage concerned with（）

A．Objects.
B．Intensity.
C．Rate.
D．Frequency.

单项选择题Where is the noise pollution most serious according to the passage（）

A．In streets.
B．In airports.
C．In subway stations.
D．In concerts.