单项选择题

The cause for the heat in the interior of the earth is ______.

A．not determined
B．the great pressure of the earth
C．radioactive elements
D．the heat remaining from the formation of the earth
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单项选择题
From the information given in the passage, most minerals would melt fastest ______.
A．at 4,000'F, 5,000 feet below sea level
B．in the absence of oxygen
C．at 4,000'F, 5,000 feet above sea level
D．at the exact center of the earth at 4,000'F
单项选择题
In relation to the earth, the sun will move
A．7,000 miles per hour
B．fifteen degrees in one hour
C．1/48th of the world's circumference
D．twice as far as Polaris
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