由曲线x2=4y，x2=-4y，x=4，x=-4围成的图形绕y轴旋转一周所得旋转体的体积为Vl；满足x2+y2≤16，x2+（y-2）2≥4，x2+（y+2）2≥4的点（x，y）组成的图形绕y轴旋转一周所得旋转体的体积为V2，则（）
A．V1=(1/2)V2
B．V1=(2/3)V2
C．V1=V2
D．V1=2V2
参考答案：C
解析：
如题图，两图形绕y轴旋转所得旋转体夹在两相距为8的平行平面之间，用任意一个与y轴垂直的平面截这两个旋转体，设截面与原点距离为|y|，则所得截面面积
S1=π(42-4|y|)，
S2=π(42-y2)-π[4-(2-|y|)2]=π(42-4|y|)∴S1=S2
由祖暅原理知，两几何体体积相等，
∴V1=V2．故选C．
| 阅读理解。 | |||||||||||||||||||||||||||
| As we know, some children live in the countryside, and some live in the city. Their lives are a little different, but they also have many of the same dreams.
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| 1. The survey was done among the ________ between the countryside and the city. | |||||||||||||||||||||||||||
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| A. parents B. students C. teachers D. drivers | |||||||||||||||||||||||||||
| 2. The children in the city usually do ________ according to the survey. | |||||||||||||||||||||||||||
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| A. cooking B. cleaning C. washing D. no housework | |||||||||||||||||||||||||||
| 3. About ________ of children in the countryside have good eyesight, while ________ of children in the city have good eyesight. | |||||||||||||||||||||||||||
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A. 55%; 25% | |||||||||||||||||||||||||||
| 4. Which is NOT mentioned in the survey? | |||||||||||||||||||||||||||
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| A. Homework. B. Subjects. C. Dream jobs. D. After-class activities. | |||||||||||||||||||||||||||
| 5. Which of the following is RIGHT according to the survey? | |||||||||||||||||||||||||||
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| A. A classroom in the countryside often has TV sets. B. Children in the countryside often join the school clubs. C. Children in the city often have much homework to do. D. Children in the city often have big families. |