What are the four most important ways a firm becomes a monopoly? The four main reasons a firm becomes a monopoly are:
A. the government blocks entry, control of a key resource, network externalities, and economies of scale.
B. antitrust legislation, control of a key resource, no close substitutes, and economies of scale.
C. the government blocks entry, control of a key resource, network externalities, and diseconomies of scale.
D. antitrust legislation, control of a key resource, arbitrage, and economies of scale.
E. the lack of patents and copyrights, control of a key resource, network externalities, and economies of scale.