A monopolist may enjoy abnormal profit only if its
Marginal cost exceeds marginal revenue
Demand curve is perfectly elastic
Expenditure on advertisement increases
Price exceeds average total cost
Correct answer is D
A monopolist may enjoy abnormal profit only if its price exceeds average total cost. This is because a monopolist is the only producer in the market, and they can therefore set the price of their product. If the price exceeds average total cost, the monopolist will be making a profit.