—Yes. My grandfather was one of them. He went there in his .
A:1990s; twenties
B:1990s; twenty
C:the 1990s; twentieth
D:the 1990s: twenties
①80℃时,甲物质的溶解度是____;
②t2℃时,把甲、乙、丙三种物质的饱和溶液降温到t1℃,溶质质量分数不变的是____;
③若要让乙物质从它的饱和溶液中全部结晶析出,应采取的方法是____.