钢轨的发展方向是（）、（）和（）。
参考答案：重型化；强韧化；纯净化
供试品与硝酸共热，得黄色产物，放冷后加醇制氢氧化钾少许，即显深紫色。此反应可鉴别的药物是
A．盐酸麻黄碱B．硫酸阿托品C．盐酸吗啡D．硫酸奎宁E．硝酸士的宁
How many Olympic employees and volunteers were at the 23rd Olympic Games
A. 14,300.B. Approximately 103,000C. More than 43,000.
