Which of the Following Best Describes Real-World U.S.markets

Which of the following best describes real-world U.S.markets?

A) In most markets,the firms face steep demand curves for their output.
B) They combine characteristics of monopolistic competition,oligopoly,and monopoly.
C) Effective competition exists in only about 25 percent of those markets.
D) The dominant share of U.S.manufacturing output is produced by firms with the power to vary their prices over a wide range.
E) Perfect competition is useful as a model for very few U.S.markets.