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.