Which of the following correctly represents the variation of electric potential (V)of a charged spherical conductor of radius (R) with radial distance (r) from the center? 

We know that electric potential at radial distance r from the from the center of a spherical charger conductor is given by 

$\mathrm{V}=\frac{\mathrm{KQ}}{\mathrm{R}},\mathrm{r}\le \mathrm{R}$

         $\frac{\mathrm{KQ}}{\mathrm{r}},\mathrm{r}>\mathrm{R}$

This shows that potential at a point inside the sphere is constant and from r > R, V keeps decreasing with increase in r.