分类法是化学学习和研究的重要方法之一。下列分类正确的是

A．非金属元素：Hg、O、Si

B．混合物：空气、石油、冰水共存物

C．盐：KMnO₄、NaNO₂、CaCO₃

D．金属材料：生铁、玻璃钢、不锈钢

They have decided to build a monument ______ those who died in the great earthquake.

A．in place of

B．in search of

C．in charge of

D．in memory of