If on the concentric hollow spheres of radii \[r\] and \[R(>r)\] the charge \[Q\] is distributed such that their surface densities are same then the potential at their common centre is [IIT 1981; MP PMT 2003]

• A.                    \[\frac{Q({{R}^{2}}+{{r}^{2}})}{4\pi {{\varepsilon }_{0}}(R+r)}\]
• B.                                      \[\frac{QR}{R+r}\]
• C.                    Zero                                 
• D.            \[\frac{Q(R+r)}{4\pi {{\varepsilon }_{0}}({{R}^{2}}+{{r}^{2}})}\]