A natural monopolya. exists when many sellers experience lower average total costs than potentialcompetitors do. b. exists when a firm has sole ownership of a natural resource. c. is an example of a government-created barrier. d. is needed to make a profit in the long run. e. exists when a single seller experiences lower average total costs than any potentialcompetitor.

e. exists when a single seller experiences lower average total costs than any potential competitor.

Explanation:

A monopoly is a market structure which is typically characterized by a single-seller who sells a unique product in the market by dominance. This ultimately implies that, it is a market structure wherein the seller has no competitor because he is solely responsible for the sale of unique products without close substitutes. Any individual that deals with the sales of unique products in a monopolistic market is generally referred to as a monopolist.

For example, a public water supply company is an example of a monopoly because they serve as the only source of water provider to the general public in a society.

A natural monopoly exists when a single seller experiences lower average total costs than any potential competitor because of the very high start-up or initial cost and economy of scale.