A thin metallic spherical shell contains a charge Q on it . A point charge q is placed at the centre of the shell and another charge $\;q_{1}\;$ is placed outside it as shown in figure . All the three charges are +ve . The force on the charge at centre is

Question

$(a)\;towards\;left\qquad(b)\;towards\;right\qquad(c)\;zero\qquad(d)\;None\;of\;these$