Economists study market structures that fall between the two extremes of perfect competition and monopoly for all of the following reasons except​: A. Realistic models of market structure lie somewhere between perfect competition and monopoly. B. Studying the interaction between firms allows us to learn about the nature of competition and how prices are set. C. Counting the number of firms tells us whether the market is competitive. D. Additional models are necessary to help answer questions about how many firms are necessary to make a market competitive.