Two insulated charged spheres of radii $R_{1}$ and $R_{2}$ having charges $Q_{1}$ and $Q_{2}$ respectively are connected to each other, then there is
(a) no change in the energy of the system
(b) an increase in the energy of the system
(c) always a decrease in the energy of the system
(d) a decrease in energy of the system unless $q_{1} R_{2}=q_{2} R_{1}$