Answer:
The decisions of one seller often influence the price of products, the output, and the profits of rival firms.
Step-by-step explanation:
An oligopoly is a market structure where there are only a few sellers. Therefore, around two or more firms have control over the market. Collectively, they can influence the prices and supply.
This ultimately results in high-level competition between these sellers. Since there are a few sellers in the oligopoly structure, each of these company's profit levels not only depends on the decisions made by them but also on the decisions made by their rival firms.
Hence, option no. 3 "the decisions of one seller often influence the price of products, the output, and the profits of rival firms" is correct.