b
In a conductor, potential is same everywhere
$\therefore $ Potential at $\mathrm{A}=$ potential at centre
$=\mathrm{V}_{\text {due to } \mathrm{p}}+\mathrm{V}_{\text {due to induced charges }}$
$=\frac{\mathrm{kp}}{(\mathrm{rsec} \phi)^{2}}+0=\frac{\mathrm{kp} \cos ^{2} \phi}{\mathrm{r}^{2}}$