What effect might the government have on oligopolies? In oligopolies, the government might A. promote competition with a patent comma which grants exclusive rights to product a good. B. impose barriers to entry with a tariff to limit foreign competition. C. impose barriers to entry with a copyright, which allows only the government to supply a good or service. D. impose barriers to entry with a free-trade agreement with another country to promote competition. E. promote competition by allowing large firms to lobby state legislators and members of Congress for favorable laws.