Which Statement Is True

Which statement is true?

A) If the Metropolitan Opera had every opera star in the world under contract,it would be considered a monopoly because it had control over an essential resource in its business.
B) There is no way to distinguish between the long run and the short-run if a monopoly is making a profit.
C) Until the early 1960s,the National Football League had control of an essential resource,star football players,and was therefore able to maintain its monopoly status until the American Football League started drafting college stars in the early 1960s.
D) All of the statements are true.