If Either the Production or Consumption of a Good Generates

If either the production or consumption of a good generates an external benefit, then the:

A) social demand curve will lie to the right of the private demand curve.
B) social demand curve will lie to the left of the private demand curve.
C) social marginal cost curve will lie to the left of the private marginal cost curve.
D) social marginal cost of the good will equal zero.