Which of the following is true regarding the similarities and differences in monopolistic competition and monopoly ?

A. the monopolist faces a downward-slog demand curve while the monopolistic competitor faces an elastic demand curve
B. the monopolist charges a price above marginal cost while the monopolistic competitor charges a price equal to marginal cost
C. The monopolist makes economic profits in the long run while the monopolistic competitor makes zero economic profits in the long run
D. Both the monopolist and the monopolistic competitor operate at the efficient scale