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单选题
A circle has an area of A, A second circle has a diameter four times that of the first circle. What is the area of the second circle?
A

2A

B

4A

C

8A

D

16A

E

32A

参考答案

参考解析
解析：
设圆1的半径为r，所以A=πr2，所以圆2的半径为2r，面积=2*π*(2r)2=16πr2=16A，故本题应选D项。
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