Question

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.

Explanation:

An oligopoly is a market structure with few firms. In the case of phone makers using one of two popular operating systems, it shows a limited - firm situation (as there are likely only a couple of dominant operating systems, and phone makers are restricted in their choices). The other options like the tire producer (demand already met - could be more competitive), running shoes (patent issue - more about barriers like patents), and power tools (low - price strategy - could be more competitive entry) do not as clearly represent the few - firm characteristic of an oligopoly.

Answer:

A new phone makers use one of two popular operating systems.