Why are batteries made by firms in oligopoly? Why isn't there monopolistic competition in that industry? Batteries are made by firms in oligopoly and not in monopolistic competition because _______. A. each firm faces a downward-sloping demand curve and the HHI is less than 2,500 B. legal barriers to entry exist in the market for batteries C. consumers demand differentiated products in the market for batteries D. economies of scale exist and the demand for batteries limits the number of firms that can make a profit in the market