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

1. Edge centres of the cube
2. Corners as well as face centres of the cube
3. Centres of faces of the cube
4. Corners of the cube

The correct option is B 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 $6:6$