A metal sphere of radius $r_1$ is charged to potential $V_1$ and enclosed in thin spherical shell. If metal sphere is connected to shell by a conductor the potential of shell will be :

Question

$(A)\;V_1 \\ (B)\;\frac{V_1r_2}{r_1} \\ (C)\; \frac{V_1r_1}{r_2} \\ (D)\;\frac{V_1r_1}{r_1+r_2}$