At the end of last year, New York’s stock market fell, ______ a global financial crisis. A. setting off B. driving off C. giving off D. laying off 答案:A根据下列要求,写出有关反应方程式(1)治疗胃酸过多(一个)____________(2)工业上用赤铁矿石炼铁________________(3)测定空气中氧气含量的原理_____________(4)氢氧化钠要密封保存的原因______________