答
It's raining hard. You should take _____ umbrella or _____ raincoat with you.
混合物成分
除杂试剂
化学方程式
(i)铜粉中混有铁粉
____
(ii)铁粉中混有铝粉
(iii)Al2O3中混有Al(OH)3
(iv)FeCl3溶液中混有FeCl2