单项选择题

A pigment called melanin protects the（）layers of skin from sun rays.

A．under
B．below
C．underlying
D．underneath

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单项选择题
Rice is the（）food of most Southeast Asians.

A．common
B．general
C．staple
D．popular
单项选择题
It was from the Lowell Laboratory that the ninth（）, Pluto, was sighted in 1930.

A．planet
B．constellation
C．stardom
D．satellite
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