题目

侯氏制碱法中，对母液中析出NH4Cl无帮助的操作是（     ） A．通入CO2        B．通入NH3        C．冷却母液         D．加入食盐 答案：A Yesterday a reporter asked 10 students at Hilltop School_________last weekend. A. what did they do        B. what were they doing        C. what they did