We feel an object is heavy
A. because weight is a fixed quality in an object.
B. because they are far away from the centre of the earth.
C. because of the earth's strong attraction for them.
D. because they are not taken away from the surface of the earth.
According to the passage, how many miles is the earth's diameter？
A. 2,000.
B. 4,000.
C. 8,000.
D. 16,000.
Advance in science more often than not encounters powerful opposition, __________ Darvin's
A. as was the ease with
B. such as the case of
C. as it did with
D. as in the ease of
正确答案是（）
A. calls out
B. calls over
C. calls in
D. calls for
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