题目

— I spent two weeks in London last summer.    — Then you must have visited the British Museum during your stay, ________ you?      A. mustn’t                    B. haven’t              C. didn’t                       D. hadn’t 答案：C40g溶质的质量分数为20%的食盐水中，含有食盐              g；含有水             g；如果再加入60g溶质的质量分数为10%的食盐水，则混合后溶液中溶质的质量分数为               。