Main Answer:
a) Monopoly
b) Perfectly competitive
c) Monopolistically competitive
Therefore, the correct answer is a, b, c.
Step-by-step explanation:
The first description, "Unique products without close substitutes," aligns with the characteristics of a monopoly. In a monopoly, a single seller dominates the market and offers a product with no close substitutes, giving the firm significant pricing power.
The second description, "Similar products," corresponds to a perfectly competitive market structure. Perfect competition is characterized by numerous buyers and sellers dealing in homogeneous (similar) products, where no single entity has control over the market price.
The third description, "Differentiated products," characterizes monopolistically competitive markets. In monopolistic competition, firms offer products that are similar but not identical, allowing for product differentiation and competition based on factors other than price.
In summary, the unique products without substitutes align with a monopoly, similar products fit perfectly competitive markets, and differentiated products are indicative of monopolistically competitive markets.
Therefore, the correct answer is a, b, c.