What term describes a company that exclusively owns all businesses selling the same product?

The correct term that describes a company that exclusively owns all businesses selling the same product is "monopoly." A monopoly occurs when a single entity has complete control over a particular product or service in the market. This means that no other competitors exist to offer the same product or service, allowing the monopolistic company to set prices and dictate market conditions without any external competition. This situation can lead to a lack of choices for consumers and can affect pricing structures across the board.

In contrast, an oligopoly involves a few firms dominating the market, but there is still some competition among them. A duopoly consists of only two firms controlling the majority of the market share for a given product or service, and competition refers to the presence of multiple companies providing similar products that compete for the same customers. These distinctions highlight the unique characteristics of a monopoly, making it the correct answer for the question provided.