下列各变化中属于原电池反应的是（ ）
A．在空气中金属铝表面迅速氧化形成保护层
B．镀锌铁表面锌有划损时，也能阻止铁被氧化
C．红热的铁丝与冷水接触，表面表成蓝黑色保护层
D．锌和稀硫酸反应时，加入少量的CuSO4溶液可使反应加快
BD
铝是活泼的金属，A中是化学腐蚀。红热的铁丝与冷水接触发生的化学腐蚀，选项BD才是通过原电池反应实现的，答案选BD。
BEIJING—The sky is gray and air smells strange. It’s another day of smog. On Saturday, heavy haze（霾）still covered north and east China. Highways were closed and couldn’t take off on time. The smoggy weather the country’s land from north to south, including Beijing, Hebei, Shandong, and 6 other provinces. People could only see clearly than 50 meters in some areas. Cities Shanghai and Nanjing have been covered by the gray sky for the past several days. Many walkers in the street had to wear . In the Lukou airport in Nanjing, more than 60 flights were canceled(取消) on Saturday the haze, which also made primary and middle schools and kindergartens stop on Thursday and Friday in Nanjing. The office worker of Environmental Protection said earlier this week that there were several reasons behind the widespread haze: unpleasant weather conditions making difficult for smog to disappear, motor vehicle exhaust（尾气）, and coal use for winter heating. To fight pollution, the Chinese government now plans to clean up the air by cutting coal use, some factories, and removing 6 million old cars from the roads. “We must face up to the facts,” said Yan Naiqiang, a professor of environmental science at Shanghai Jiao Tong University. “The treatment of smog will be a long fight. From now on, if we use buses or cars less and do more riding, we believe a clear sky is not a faraway dream.”
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