As our country has realized the problem and taken some measures, the price of medicine has _____ and

poor people can also afford good medicine. [ ]

A. gone down

B. brought down

C. turned down

D. cut down

下表列出了硝酸钾在不同温度下的溶解度：

（2）在20℃时，向100g水中加入30g硝酸钾，形成的硝酸钾溶液是______（填“饱和”或“不饱和”）溶液，此时，硝酸钾溶液的溶质质量分数为______．

（3）请依据上表给定的数据在右边的表格中绘制溶解度曲线

（4）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______g．