A:用食醋除去暖瓶内的水垢
B:鸡蛋白溶液中加入硫酸铵饱和溶液后析出白色沉淀
C:淀粉溶液中加碘水变蓝
D:棉花织品和羊毛织品:分别灼烧闻气味
请据此回答:
My dog is lost.I put its pictures newspapers and television to find it.
求证:BC是⊙O的切线。