题目

Mark Twain was a great writer. He was from the USA. He was born in 1835. He was also a famous speaker. He was famous for his sense of humour. Many people liked to listen to him , because he liked to tell some interesting stories to make people laugh all the time. One day Mark Twain was going to a small town because of his writing. Before he was going to leave, one of his friends said to him that there were always a lot of mosquitoes (蚊子) in the town and told him that he’d better not go there. Mark Twain waved his hand and said, “It doesn’t matter. The mosquitoes are no relati19．下列实验操作能达到实验目的是（　　）选项实验目的实验操作A验证 NaCl 溶液中混有盐酸取少量溶液，滴加无色酚酞溶液B比较 Fe、Cu、Ag的金属活动性铁丝浸入CuSO4 溶液，铜丝浸入AgNO3溶液C除去铁制品上的铁锈将铁制品浸泡在足量的稀硫酸中D除去粗盐中的难溶性杂质将粗盐研碎、溶解、蒸发A．AB．BC．CD．D