Perfect competition is defined as: A. many firms, each being small relative to the industry and producing virtually identical products, and in which at least one firm is large enough to have significant control over prices. B. many firms, each being small relative to the industry and producing highly differentiated products, and in which no firm is large enough to have any control over prices. C. few firms, each being large relative to the industry and producing virtually identical products, and in which one firm is large enough to have some control over prices. D. many firms, each being small relative to the industry and producing virtually identical products, and in which no firm is large enough to have any control over prices.