If There Are Barriers to Entry into a Market,it Is

If there are barriers to entry into a market,it is possible for the existing firm(s) to earn positive economic profits.All of the following explain this except:

A) new firms cannot enter to take advantage of the profits.
B) resource immobility.
C) it is possible for a firm in this situation to charge any price it wants and thus preclude anyone else from entering.
D) competition does not erode profits the way it would under perfect competition.