Which situation could be the best example of an oligopoly?

a new producer of power tools has entered the market and is relying on low prices to attract consumers.
a new producer of a smart phone operating system is trying to enter the market but cannot because most cell phone makers use one of two popular operating systems.
a new producer of running shoes is trying to enter the market but cannot because of an existing patent.
a new producer of tires has entered the market and found that demand is already being met.

Value economics capital scarcity opportunity cost wealth labor trade-offs standard of living good a. condition of not having enough resources to produce all the things people want b. alternative choices made by consumers in the marketplace c. sum of those economic products that are tangible, scarce, useful, and transferable d. tools, equipment, machinery, and factories used in the production of goods and services e. tangible item that is economically useful or that satisfies an economic want f. quality of life based on the ownership of the necessities and luxuries that make life easier g. people with all their efforts, abilities, and skills h. cost of the next-best alternative use of money, time, or resources when one choice is made rather than another i. study of how people try to satisfy their needs through the careful use of scarce resources j. worth that can be expressed in dollars and cents