The correct option is D Kq4
We know that, net electric field inside a conductor is zero
i.e. (−−→Enet)@O=0
Since the net electric field at the center is the sum of the electric fields due to charge q and due to the induced charge on the sphere,
−−→Enet=−→Eq+−−→Eind=0
⇒−−→Eind=−→Eq
∴|−−→Eind|=Kq(2)2=Kq4
Hence, option (d) is the correct answer.