下列归类正确的是() 选项归类物质 A黑色固体高锰酸钾、四氧化三铁、炭黑 B可直接加热的仪器试管、蒸发皿、玻璃棒 C刺激性气味的气体氨气、二氧化硫、氦气 D缓慢氧化铁丝生锈、农家肥的腐熟、天然气燃烧 A . A B . B C . C D . D 答案:BAs it ______ that more and more cars use clean energy, the air is becoming cleaner in many cities across China.A. encourages B. will encourage C. is encouraged D. will be encouraged