Which of the following statements is true? I. The source of…

Which of the following statements is true? I. The source of market power for monopolistically competitive firms is their ability to differentiate products. II. In the short run, the monopolistically competitive firm sets price and output in a manner similar to a monopolist. III.  In the long run, the monopolistically competitive firm can earn economic profits, but not as large as those made by a monopoly firm. IV. Oligopolies typically earn normal profits.