A charged +Q is uniformly distributed in a spherical volume of radius R . A particle of charge +q and mass m projected with velocity $\;v_{0}\;$ from the surface of the spherical volume to its centre inside a smooth tunnel dug across the sphere . The minimum value of $\;v_{0}\;$ such that it just reaches the centre of the spherical volume is

Question

$(a)\;\sqrt{\large\frac{kQq}{2mR}}\qquad(b)\;\sqrt{\large\frac{kQq}{4mR}}\qquad(c)\;\sqrt{\large\frac{2kQq}{4mR}}\qquad(d)\;\sqrt{\large\frac{kQq}{mR}}$