① How much is it? ____ A. OK.Here you are.
② Can I try them on? ____ B. It's $89.
③ Is it too expensive? ____ C. It's very pretty.
④ How do you like this skirt? ____ D. Yes,it is.
“根深叶茂,树干粗壮”,这是对一棵大树的整体性描述.下图所示的结构层次中,属于器官的是( )
①称取一定质量的该白色粉末加足量水溶解,得无色溶液A;
②在无色溶液A中加入过量氯化钡溶液,充分反应后过滤,分别得无色溶液B和白色沉淀C;将白色沉淀C洗涤,烘干后称得质量为19g;
③在19g白色沉淀C中加入足量的稀硝酸,沉淀部分消失,并有气泡冒出;
④在无色溶液B中滴加硝酸银溶液和稀硝酸,产生白色沉淀;
根据上述实验现象判断,下列说法正确的是( )