Co-ordination number of a crystalline solid is

Question

$\begin{array}{1 1} \text{(a) Number of particles in the unit cell} \\ \text{ (b) Number of nearest neighbours of a particle} \\ \text{ (c) Number of octahedral voids in a unit cell} \\ \text{ (d) Number of tetrahedral voids in a unit cell} \end{array}$