One Difference Between Perfect Competition and Monopolistic Competition Is That

One difference between perfect competition and monopolistic competition is that

A) in perfect competition, firms cannot earn a long-run economic profit
B) in perfect competition, firms take full advantage of economies of scale in long-run equilibrium; in monopolistic competition, firms do not
C) only under perfect competition is there ease of entry and exit
D) in monopolistic competition, the firm's demand curve is horizontal; in perfect competition, the firm's demand curve slopes downward
E) in perfect competition, there are many firms; under monopolistic competition, there are few firms