In the Long Run,economic Profit Earned by a Monopolistically Competitive

In the long run,economic profit earned by a monopolistically competitive firm _____

A) is zero because of the lack of barriers to entry.
B) is zero because of the production of homogenous goods.
C) may be positive because of strong barriers to entry.
D) may be positive because of product differentiation.
E) may be positive because of advertising and product promotion.