In a Free Market with Pollution and No Government Intervention,the

In a free market with pollution and no government intervention,the market equilibrium quantity of pollution reduction is reached when:

A) pollution reduction is zero.(No pollution is reduced.)
B) the social marginal cost of reduction equals twice the marginal benefit of reduction.
C) the social marginal benefits of reduction equal its social costs.
D) the social marginal benefits of reduction equal its social marginal costs.