圆柱体的侧面积扩大到原来的8倍，高扩大到原来的2倍，则底面半径扩大到原来的倍数是()．
A. 2
B. 4
C. 8
D. 2/π
E. 8/π
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立方体的边长扩大为原来的2倍后的体积比原来的体积大()倍．
A. 5
B. 6
C. 7
D. 8
E. 9
Alice______her father that both she and her husband would be happy if he would live with them.
A. convinced
B. required
C. pledged
D. reinforced
The main idea of the first paragraph is that______.
A. the generation gap suddenly appeared
B. the generation gap is a feature of American life
C. how people can reduce the generation gap
D. many critics argue over the nature of the generation gap
如果两商品是互补商品，那么消费者的无差异曲线的斜率可以是()。
A. 0
B. 1
C. 2
D. 3
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