The correct option is D Octahedral
In NaCl,Cl− ions forms fcc structure lattic. Thus, Cl− present at the corners and face centres of the cube.
Here, Na+ ions occupies all the octahedral voids. The octahedral voids are present at the edge centres and body centre of the unit cell. The tetrahedral voids of this ccp arrangement is vacant.
Experimentally, the radius ratio of NaCl is comes out to be 0.51
Since,
0.414<0.51<0.732
The coordination number of NaCl is 6.
Thus, Na+ occupies the octahedral voids.