Concept:Oligopoly is a market structure dominated by a small number of large sellers.Explanation:In an oligopoly, the number of sellers is small, so each seller holds significant market power.These few sellers may compete or collude, and their decisions affect one another.New firms find entry difficult because of high barriers such as capital requirements, patents, or control of resources.Therefore, the key feature highlighted in the question is the availability of few sellers.Answer:A. few sellers