Please help with answering the following two questions

Question 5 (1 point) An industry or sector made up of a small number of companies, each of which thinks carefully of the likely reactions of its rivals in making price-output decisions is called: O monopolistic competition O perfect competition O monopoly O oligopoly Question 6 (1 point) A market in which the entire demand for a good or service can be fulfilled at the least expense by a single firm is a: 0 perfect market 0 contestable market 0 horizontal market 0 natural monopoly