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问题 选择题
关于x的一元二次方程x2-mx+2m-1=0的两个实数根分别是x1、x2，且x12+x22=7，则（x1-x2）2的值是（   ）
A.1
B.12
C.13
D.25
答案

答案：C

单项选择题

Which of the following fiscal policy models is most likely to support the conclusion that the adjustment of money wages to restore full-employment equilibrium is rapid and that without the distorting effects of taxes, long-run equilibrium real output would increase with increases in the labor force and accumulated capital, and with improvements in technology（）

A. Classical.

B. Keynesian.

C. Supply-side.
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单项选择题

提高金属回收率是降低（）品位为前提。

A．矿浆

B．尾矿

C．原矿
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