In Comparing the Economic Structures of Different Types of Professional

In comparing the economic structures of different types of professional sports, we see that:

A) sports such as tennis and golf are salary-based, while sports such as football, baseball, and basketball are winnings-based.
B) the income of athletes in a winnings-based sport tends to be more secure and predictable than the income of athletes in a salary-based sport is.
C) a single major boxing event can generate more revenue than most big-league professional sports teams other than those in the NFL earn in a season.
D) unlike major professional sports leagues in North America, NASCAR has not had a monopolistic structure.