An electric dipole is situated in an electric field of uniform intensity E whose dipole moment is p and moment of inertia is I. If the dipole is displaced slightly from the equilibrium position, then the angular frequency of its oscillations is

(1) ${\left(\frac{pE}{I}\right)}^{1/2}$

(2) ${\left(\frac{pE}{I}\right)}^{3/2}$

(3) ${\left(\frac{I}{pE}\right)}^{1/2}$

(4) ${\left(\frac{p}{IE}\right)}^{1/2}$