The cartel of oil-producing nations (OPEC) once controlled about 80% of the world petroleum market, but OPEC's market share has declined to about half of its former level. This outcome is a good example of how firms may have:
A) relatively high short-run monopoly power that strengthens in the long run.
B) relatively high short-run monopoly power that declines in the long run.
C) relatively low short-run monopoly power that strengthens in the long run.
D) relatively low short-run monopoly power that declines in the long run.