实现总供求关系的基本平衡，短期应( )。
A．减少国内需求
B．扩大国内需求
C．扩大出口
D．减少出口
参考答案：C
下列关于反应原理及对应说明的表述正确的是 [ ]
A．BaCO3与所有强酸反应的离子方程式都可表示为BaCO3+2H+=Ba2++H2O+CO2↑
B．工业上用于刻蚀铜制印刷电路板的离子方程式是Fe3++Cu=Cu2++Fe2+
C．SiO2+CSi+CO2↑是工业制取粗硅的反应
D．由反应SO2+Cl2+2H2O=H2SO4+2HCl可知，向新制氯水中通入SO2，溶液的pH会减小
A certain ball was dropped from a window 8 meters above a sidewalk. On each bounce it rose straight up exactly one-half the distance of the previous fall. After the third bounce the ball was caught when it reached a height of exactly 1 meter above the sidewalk. How many meters did the ball travel in all ？（）
A．21
B．19
C．17
D．15
E．13
Si+CO2↑是工业制取粗硅的反应