Market structure featuring a single seller with a unique product and no close substitutes?

• A. Market structure
• B. Oligopoly
• C. Monopolistic competition
• D. Monopoly

Answer: (D)

This is about a monopoly. A monopoly exists when a single firm is the only seller in the market, offering a product with no close substitutes. Because there’s no alternative that consumers see as a good replacement, the firm can influence the price rather than take it as given by the market.

Key implications: the monopolist’s demand curve is the market demand, so the firm faces downward-sloping demand and can set higher prices than in competitive markets. Barriers to entry keep other firms out, which is why profits can persist. This contrasts with other structures: an oligopoly has a few firms competing, often with some interdependence; monopolistic competition features many firms offering differentiated products; and perfect competition has many firms selling identical products with no barriers to entry, so no single firm can set prices.