高階econ-u05-d05
In long-run equilibrium under perfect competition, firms earn:
A. Normal profit, which is zero economic profit✓ 答案
B. Guaranteed supernormal profit for every firm
C. Losses equal to total fixed cost only
D. Zero accounting profit but supernormal economic profit
解說
Free entry and exit move the market until economic profit is zero, so price equals minimum average total cost. Supernormal profit can persist only when entry is blocked.