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 axial

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} )