The social cost curve lies above the private cost curve for the producer in case of which of the…

With a negative externality such as pollution, production imposes costs on others that the producer does not pay. Marginal social cost then equals marginal private cost plus marginal external cost, $MSC = MPC + MEC$, so the social cost curve lies above the private cost curve. With a positive externality the gap runs the other way, on the benefit side.