In which of the following, cation occupies cubic void.

Both $\mathrm{AgCl}$ and $\mathrm{HgS}$ have structures similar to that of $\mathrm{NaCl}$, meaning they both contain octahedral voids. $\mathrm{LiCl}$ also has a distorted $\mathrm{NaCl}$ structure.  In ${\mathrm{NH}}_4\mathrm{Cl}$, the $C{l}^{-}$ions at the cell's corners can form hydrogen bonds with the ${\mathrm{NH}}^{+}$cation, which resides in the cubic site at the cell's center. Hence, in ${\mathrm{NH}}_4\mathrm{Cl}$ the cation ${\mathrm{NH}}^{+}$occupies the cubic void.