When a Monopolistically Competitive Industry Is in Long- Run Equilibrium

When a monopolistically competitive industry is in long- run equilibrium, the excess capacity in an individual firm is indicated by the difference between

A) price and average cost.
B) zero and the output at which the demand curve is tangent to the ATC curve.
C) the output at which ATC is at a minimum and the output at which price equals marginal cost.
D) the output at which ATC is at a minimum and the output at which marginal revenue is equal to marginal cost.
E) price and marginal cost.