有一包白色粉末，可能含有氯化钡、氢氧化钠、碳酸氢铵、氯化钠、无水硫酸铜、碳酸钙中的一种或几种．为确定其组成．进行如下实验：

①取少量该粉末置于烧杯中，未嗅到任何气味；向烧杯中加人适量的水，充分搅拌，静置后，观察到上层溶液呈无色，烧杯底部有蓝白色固体；过滤．

②向上述滤液中滴加几滴硝酸银溶液，溶液变浑浊．

③将上述滤渣投入盛有足量稀盐酸的烧杯中，充分搅拌，有无色无味的气体产生．烧杯底部有白色固体剩余．

则下列说法正确的是（　　）

如图所示，地球绕OO′轴自转，则下列正确的是（   ）

B

    Running is becoming popular these days. Many of us run for our health. Doctors say many of the health problems come from these bad habits: eating too much, drinking too much, smoking, and not taking enough exercise. Doctors tell us, "Eat and drink less, don't smoke, and exercise more."

    Running is a good form of exercise because it helps build a strong heart. It also helps most people lose weight. One 68­year­old woman runs three times a week. She runs to lose weight.

    Running is good for health in other ways, too. Many runners say running keeps colds and other small health problems away." Running is my doctor, "says one man.

    Running can also help people to relax. So today men and women of all ages enjoy running.