The correct option is D 2.88×10−3 N/C
Distance of charges from centre of dipole, l=1 mm;
Distance of point P from centre of dipole, x=5.001≈5 m;
Magnitude of charge, q=10 nC;
Here, we can see that l<<x
Therefore, the net electric field due to a dipole at an axial point is given by
So, option (d) is correct.