Questions: Because a monopoly is a price maker and prices its products in the elastic portion of the demand curve, its output is less than that required to achieve minimum average total cost. In addition, the monopoly's price will exceed its marginal cost at this level of output. Monopoly therefore creates - a revenue loss. - an efficiency loss. - greater efficiency. - a marginal loss.

The answer is the second one: an efficiency loss.

Explanation for each option:

• A revenue loss: This is incorrect. While monopolies may not maximize total revenue, the primary issue discussed in the context of monopolies is not about revenue loss but about efficiency and welfare loss.

• An efficiency loss: This is correct. Monopolies create an efficiency loss, also known as a deadweight loss, because they produce less output than would be produced in a competitive market. This results in a loss of consumer and producer surplus, as the price is higher and the quantity is lower than the socially optimal level.

• Greater efficiency: This is incorrect. Monopolies are generally less efficient than competitive markets because they do not produce at the minimum average total cost and set prices above marginal cost, leading to a deadweight loss.

• A marginal loss: This is incorrect. The term "marginal loss" is not typically used in the context of monopoly analysis. The focus is on the inefficiency and welfare loss due to the monopoly's pricing and output decisions.

In summary, a monopoly creates an efficiency loss because it restricts output and charges a higher price than would be the case in a competitive market, leading to a deadweight loss.