题目

The boy was too young to write, but he sent his father a letter and told him what had happened drawing pictures．    A．with          B．in            C．to           D．by   答案：D12．下列事实能用同一原理解释的是（　　）A．将二氧化硅分别加入到氢氧化钠溶液或氢氟酸中，固体都溶解B．向氯化钡溶液通入SO2，再加入氯水或氨水，都产生白色沉淀C．向蛋白质溶液中加入饱和醋酸钠或醋酸铅溶液，都产生白色沉淀D．蘸取烧碱和纯碱溶液分别放在无色火焰上灼烧，都产生黄色火焰