A:What can you hear, Alice?
B:What can you smell, Alice?
下列地区中,水旱灾害最为频繁的是( )
Where ____ (is, are) the pen?- It's in the bag.
工业上用铝土矿(主要成分为Al2O3,杂质为Fe2O3和SiO2)为原料冶炼铝的工艺流程之一为:下列叙述不正确的是( )