题目

如要将100g溶质质量分数为20%的硝酸钾溶液稀释成溶质质量分数为10%的硝酸钾溶液，需加入水的质量为     A．50g    B．90g      C．100g     D．200g 答案：C—Boys and girls, welcome to my home and ____.--Thank you.A. help yourself B. help yourselvesC. helps yourself D. help you