According to William Shepherd's Examination of Competitive Trends in the U.S.economy

Multiple Choice

According to William Shepherd's examination of competitive trends in the U.S.economy, a dominant firm

A) is a pure monopoly
B) is a firm with over half the market share and no close rival
C) is one of four firms that together supply more than 60 percent of the market
D) is a single firm that controls the entire market and can block entry
E) is one of four firms that work together to block entry into the market