A Perfectly Competitive Firm and a Monopoly Firm Are Alike

A perfectly competitive firm and a monopoly firm are alike in that:

A) both face horizontal demand curves.
B) both maximize profits at an output level where marginal revenue equals marginal cost.
C) both face economies of scale in the long run.
D) both earn zero economic profits in the long run.
E) both face competition in the long run because of the free entry and exit of rival firms.