Which is / are correct statement about zinc blende structure?

• A

  $\text{ The number of first neighbours of }{\mathrm{S}}^{2-}\text{ is }4$

• B

  $\text{ The maximum distance between }{\mathrm{Zn}}^{2+}\text{ is }\frac{\mathrm{a}\sqrt{3}}{2},\text{ where ' }\mathrm{a}\text{ ' }=\text{ edge length of unit cell }$

• C

  $\text{ If all tetrahedral voids are occupied by }{\mathrm{Zn}}^{2+}\text{ then C.N. of }{\mathrm{S}}^{2-}\text{ is }8\text{. }$

• D

  $\text{ If all tetrahedral voids are occupied by }{\mathrm{Zn}}^{2+}\text{ then C.N. change from }4:4\text{ to }8:8\text{. }$