The general formula of an ionic compound crystallizing in antifluorite structure is

The general formula of an ionic compound crystallizing in antifluorite structure is ${\mathrm{A}}_2\mathrm{B}$.

Cations and anions are arranged in the anti-fluorite structure in the opposite direction from the fluorite structure. 

 The structure of ${\mathrm{Na}}_2\mathrm{O}$ is an antifluorite. I The ${\mathrm{O}}^{-2}$ ions form a cubic close-packed lattice (fcc structure) in the crystal structure of ${\mathrm{Na}}_2\mathrm{O}$, while the ${\mathrm{Na}}^{+}$ ions fill all of the tetrahedral spaces.

(ii) There are 8 ${\mathrm{Na}}^{+}$ ions in contact with each oxide ion, ${\mathrm{O}}^{-2}$ ion, and 4 oxide ions with each ${\mathrm{Na}}^{+}$ ion.${\mathrm{Na}}_2\mathrm{O}$ has 4:8 coordination as a result.

${\mathrm{Na}}_2\mathrm{S}$ are  example.

Hence the option C is correct.