How will you distinguish between the following pairs of terms:
$(i)$ Hexagonal close-packing $(hcp)$ and cubic close-packing $(ccp)$?

(N/A) $(i)$ In $hcp$,the third layer is placed over the second layer such that the spheres of the third layer occupy the tetrahedral voids of the second layer. This results in an $ABAB...$ pattern of layers,where the spheres of the third layer are directly above the spheres of the first layer.
In $ccp$,the third layer is placed over the second layer such that the spheres of the third layer occupy the octahedral voids of the second layer. This results in an $ABCABC...$ pattern of layers,where the spheres of the fourth layer are directly above the spheres of the first layer.