Monopoly is unlike perfect competition in that

a. a monopolist’s price is greater than marginal cost.

b. there are no barriers to entry into a monopoly industry.

c. a monopolist earns an economic profit only if its price is greater than ATC.

d. all of the above are ways in which monopoly is unlike perfect competition.

e. (a) and (b), but not (c), are ways in which monopoly is unlike perfect competition.