The correct option for the number of tetrahedral and octahedral voids in a hexagonal primitive unit cell is:

The packing efficiency of simple cubic $(sc)$, body-centred cubic $(bcc)$ and cubic close packing $(ccp)$ lattices follow the order:

Percentage of free space in a body-centred cubic unit cell is ................ $\%$

$A$ solid compound is formed by atoms of $A$ (cations),$B$ (cations),and $O$ (anions). Atoms of $O$ form an $hcp$ lattice. Atoms of $A$ occupy $25\%$ of the tetrahedral voids,and atoms of $B$ occupy $50\%$ of the octahedral voids. What is the molecular formula of the solid?

$A$ compound is formed by elements $A$ and $B$ which crystallizes in a $CCP$ structure. Atoms of $A$ are at the corners and atoms of $B$ are at the face centers. If two atoms of $A$ are missing from the unit cell,what is the molecular formula of the compound?

Which crystal lattice has the maximum packing efficiency?