21) In which market structure is it possible to earn short-run economic profits?

monopoly and monopolistic competition

monopoly

perfect competition, monopoly, and monopolistic competition

perfect competition

23) A characteristic that distinguishes monopoly from oligopoly is

the lack of close substitutes.

many buyers and sellers.

long-run economic profits.

barriers to market entry.

24)In a perfectly competitive industry, short-run economic profits will lead firms to _____ the market, causing market price to _____.

enter; decrease

exit; decrease

enter; increase

exit; increase

28)According to federal judge and economist Richard Posner, we should repeal all the old antitrust laws and replace them with a simple statute that prohibits unreasonably anticompetitive practices.

True

False