Answer: b. produces economic profits in both the long run and the short run.
Step-by-step explanation:
Monopolies sell at a price that results from the quantity where marginal revenue equals marginal costs as this maximises profits.
Monopolies have their marginal revenue lower than their demand curve so the point where the profit maximising quantity intersects with the demand curve will result in a price above the marginal cost of the good which means that they are able to make economic profits in the short run.
Monopolies are able to maintain this trend in the long run as well because there will be barriers to entry dissuading other competitors from coming in.