In a contestable market, If the incumbent charges the monopoly price PM and earns a positive economic profit, then ( )

A、the incumbent can deter entry.
B、the potential entrant will have an incentive to enter the market and charge a price above PM.
C、the potential entrant will have an incentive to enter the market and charge a price equal to PM.
D、 the potential entrant will have an incentive to enter the market and charge a price below PM.