b

$\text{Net Electric Field inside conducting sphere is }= 0$

$\text{ Since conducting sphere is a equipotential surface}$

$\text{Potential at any point inside the sphere is same as that at the surface}$

$\text{Net induced charge at the surface of conducting sphere is zero}$

$\text{Net Potential at centre of sphere is only due to charge q } V= \frac{q}{4\pi\epsilon_0 r}$.