One Difference Between the Long Run and the Short Run

Multiple Choice

One difference between the long run and the short run in a perfectly competitive industry is that:

A) economic profits in the long run are always greater than they are in the short run.
B) economic profits in the short run are always greater than they are in the long run.
C) firms necessarily earn zero economic profit in the long run but may earn positive or negative economic profit in the short run.
D) firms necessarily earn positive economic profit in the long run but may earn positive or negative economic profit in the short run.