Good books can provide us with a wide range of experiences.
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Our human friends sometimes may make us bored, but the friends in books may also be hurt by us.
A. Right
B. Wrong
设A是三阶不可逆矩阵，α,β是线性无关的两个三维列向量，且满足Aα=β，Aβ=α，则 ()．
如题14图所示，A是半径为1的圆O外的一点，OA=2，AB是圆O的切线，B是切点，弦BC∥OA，连接AC．则阴影部分的面积等于 ()．
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