Which one is the correct expression of electric potential on the axial point of a dipole whose dipole moment is p and length is 2l, at a distance of r?

Which one is the correct expression of electric potential on the axia

1.	Which one is the correct expression of electric potential on the axial point of a dipole whose dipole moment is p and length is 2l, at a distance of r?
A.	\(\frac {p}{r^2}\)
B.	\(\frac {p}{l^2}\)
C.	\(\frac {p}{(r^2-l^2)}\)
D.	\(\frac {p}{2lr}\)
Answer» D. \(\frac {p}{2lr}\)