My host family tried to cook ____ for me when I studied in New Zealand.
①将固体溶于水,搅拌后得到无色透明溶液;
②往此溶液中滴加硝酸钡溶液,有白色沉淀生成;
③过滤,将沉淀置于稀硝酸中,发现沉淀全部溶解.