Which of the following metals has an $hcp$ crystal structure?

In a solid $AB_2$,the coordination number of $A$ is $8$. It has a cubic close-packed $(ccp)$ lattice. Half of the $B$ atoms are,however,ejected from the solid. Now,the number of tetrahedral holes (voids) that remain filled is:

In the closest packing of atoms,there are

If the anions $(A)$ form hexagonal closest packing and cations $(C)$ occupy only $2/3$ of the octahedral voids in it,then the general formula of the compound would be

Identify the types of voids represented by the structures $I$,$II$,and $III$ in the given image.

In the face-centered unit cell,the lattice points are present at