Iron Exhibits Polymorphism, the Ability of a Solid Material to Exist

Multiple Choice

Iron exhibits polymorphism, the ability of a solid material to exist in more than one crystal form.At low to moderate temperatures, it adopts a bcc structure; at temperatures above 913 $\degree$ C, it adopts an fcc structure.Silicon carbide also has polymorphs, including the wurtzite form with abab packing and the sphalerite form with abcabc packing.Which of the following statements is NOT correct?

A) The bcc and fcc forms of iron probably have the same densities.
B) The packing efficiency of iron atoms in the bcc form is lower than that of the fcc form.
C) The two silicon carbide polymorphs probably have the same densities.
D) The packing efficiencies of the two silicon polymorphs are probably the same.
E) Both SiC polymorphs are based on hexagonal packing of atoms.