The $C{l}^{-}$ ions in the of NaCl lattice structure are present at:

The correct option is C Corners as well as face centres of the cube
In $NaCl,C{l}^{-}$ ions forms fcc structure lattic. Thus, $C{l}^{-}$ present at the corners and face centres of the cube.
Here, $N{a}^{+}$ ions occupies all the octahedral voids. The octahedral voids are present at the edge centres and body centre of the unit cell.
The coordination number of $NaCl$ is $6:6$