A) Firms can earn supernormal profits in the long run.
B) Firms produce differentiated products.
C) There is free entry and exit of firms.
D) Firms have price-setting power.
For Explanation Click Here:
In a perfectly competitive market, there are no barriers to entry or exit. This allows firms to enter the market when profits are high and exit when they are incurring losses, ensuring zero economic profits in the long run.