The diagram is describing the features of pure competition (OC).
In pure competition, the market is characterized by low barriers to entry, many competing firms, and businesses selling the same product. This leads to a highly competitive market where prices are determined by the market forces of supply and demand. Each firm is a price taker, meaning they have no control over prices, and they are forced to accept the market-determined price. The low barriers to entry and presence of many competing firms lead to a highly fragmented market structure with no dominant firm or group of firms. This results in a highly competitive market where businesses are constantly innovating to stay ahead of the competition, and prices tend to be lower than in other market formats.
Option A refers to monopolies, where there is a single seller in the market with the power to set prices. Option B refers to monopolistic competition, where there are many competing firms, but they still have some power to set prices. Option D refers to oligopolies, where there are a small number of firms that together control a significant portion of the market and have the power to set prices. None of these options accurately reflects the features of pure competition described in the diagram.