Which of the following is true about the long-run equilibrium in a perfectly competitive market?

A) Firms earn positive economic profits.

B) Firms earn zero economic profits, as price equals average total cost.

C) Firms are forced to exit the market.

D) Barriers to entry prevent new firms from entering..

For Explanation Click Here:

In the long run, firms in perfect competition earn zero economic profits. The entry of new firms drives the price down until it equals average total cost, resulting in zero profits.