What best describes a monopoly?

A monopoly is characterized by the presence of a single entity that has exclusive control over the production and sale of a specific good or service in the market. This means that that particular firm is the sole provider and can dictate the terms of availability, pricing, and supply without competition. The lack of alternative suppliers enables the monopolist to maintain significant market power, which can affect market prices and consumer choices.

In contrast, other descriptions do not accurately reflect the nature of a monopoly. For instance, the presence of multiple firms sharing market power or competing on price implies the existence of competition rather than monopoly. Similarly, products being similar but not identical suggests a market with differentiated products, typically found in monopolistic competition rather than a monopoly. The idea of firms competing on price but not on the product aligns more closely with oligopolistic competition, where a few firms might dominate but still allow for some level of competition. Therefore, stating that a monopoly is characterized by a single group controlling production specifically captures the essence of this market structure.