To Reach an Economically Efficient Output Level,the Size of an Excise

Multiple Choice

To reach an economically efficient output level,the size of an excise tax imposed on a firm generating a negative externality should be

A) the firm's marginal cost.
B) the social marginal cost.
C) the difference between the social marginal cost and the firm's marginal cost.
D) the sum of the social marginal cost and the firm's marginal cost.