双集气管与单集气管比较,存在的缺点:通风差和()。
参考答案:投资大
下列物质可按溶解、过滤、蒸发的操作顺序,将它们分离开的是( )
A.酒精和水
B.氯化钾和二氧化锰
C.氯化钠和硝酸钾
D.铁粉和铜粉
—Oh!What a pretty toy car!Dad,would you be kind enough to get________for me?
—What?Didn't I buy________for you as a birthday present?[ ]
A. this; that
B. that; it
C. one; this
D. it; one