Read the given paragraph and answer the following questions.

A market refers to a system where buyers and sellers exchange goods or services, not necessarily a physical place. Market structures vary significantly. In perfect competition, there are many buyers and sellers, products are homogenous, and there are no marketing costs, with sellers being price takers. In a monopoly, there is one seller with no close substitutes, high entry barriers, and the seller acts as a price maker, facing relatively inelastic demand. Monopolistic competition involves many buyers and sellers offering differentiated products, incurring high marketing costs, with free entry, and sellers having some pricing power with relatively inelastic demand. Oligopoly features few sellers with intense competition, high marketing costs, difficult entry, and sellers as price makers. Monopsony is characterized by one buyer and multiple sellers, with entry closed to other buyers, typically seen in government defense purchases, where the buyer is the price maker.