Why Does a Pure Metal Not Crystallize in a Fluorite

Multiple Choice

Why does a pure metal not crystallize in a fluorite or antifluorite unit cell?

A) They can and do.
B) These unit cells require two types of atoms or ions with differing radii.
C) Pure metals do not crystallize; they are amorphous.
D) The atoms in pure metals move about in a sea of electrons.
E) The radius of the metal is too large.