题目

—Lily, does your family often make lanterns for Spring Festival?—No,________. We really don't know how to make them. A . always B . usually C . sometimes D . never 答案：D三种固体物质a、b、c的溶解度曲线如图所示，下列说法正确的是（　　）A.a、b、c三种物质的饱和溶液从t2℃降温到t1℃时都有晶体析出B.t1℃时三种物质的饱和溶液中溶质的质量分数大小为b＞a＞cC.t2℃时，将50g a物质加入到100g水中完全溶解形成饱和溶液D.a中混有少量b时可采取蒸发溶剂的方法提纯得到a