单项选择题

We can feel things are heavy because ______.

A．weight is a fixed quality in an object
B．they are far away from the center of the earth
C．of the earth's strong attraction for them
D．they are not taken away from the surface of the earth

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热门试题

单项选择题The way of communication ______ made use of were visible signs.

A．French
B．Roman
C．African
D．American

单项选择题The African way of communication sent messages ______.

A．in a special way
B．over a very short distance
C．by a musical instrument
D．at a rather slow speed