The correct answer is A. One seller of the product.
A pure monopoly is a market structure in which there is only one seller of a good or service. This means that the monopolist has a great deal of market power and can set prices without fear of competition.
The other options are not characteristics of pure monopoly.
B. Low barriers to entry means that it is easy for new firms to enter the market. This would not be the case in a pure monopoly, as the monopolist would have a significant advantage over any potential new entrants.
C. Close substitute products means that there are many other products that consumers can buy instead of the monopolist’s product. This would also not be the case in a pure monopoly, as the monopolist would have no close substitutes for its product.
D. Perfect information means that all buyers and sellers have complete information about the market. This would not be the case in a pure monopoly, as the monopolist would have more information about the market than its customers.