An octahedral void is surrounded by how many spheres?

In an $FCC$ unit cell,a cube is formed by joining the centers of all the tetrahedral voids to generate a new cube. Then the new cube would contain effective voids as

If a compound (oxide) has an $hcp$ arrangement and the cations $M$ occupy two-thirds of the octahedral voids,the formula of the compound is:

An ionic solid is $HCP$ of $B^{2-}$ ions and $A^{x+}$ ions are in one-fourth of tetrahedral voids. The value of $x$ should be

Which of the following metals crystallizes in a cubic closest packing $(CCP)$ structure?

In a cubic close packing,the unit cell has...