Answer:
oligopoly
Explanation:
An oligopoly is a market structure with few firms dominating a large market. It is where few sellers control a large market with many buyers. In this illustration of corn exports in the US, four companies are dominating the business.
In an oligopoly, there are likely to be other small entities operating in that industry. Each of the other firms has an insignificant market share. In this case, four companies have 80 percent of the market share. The remaining 20 percent could be controlled by many other smaller companies.