"In a long-run equilibrium, price is equal to average total cost." This statement applies to A. perfectly competitive markets, but not to monopolistically competitive markets or monopolies. B. perfect competitive and monopolistically competitive markets, but not to monopolies. C. perfect competitive markets, monopolistically competitive markets, and monopolies. D. None of the above is correct.

C) perfect competitive markets, monopolistically competitive markets, and monopolies.

Explanation:

In economics, the short run is defined as a period of time where at least one (or more) of the factors of production is fixed, e.g. production facilities, equipment, etc.

The long run refers to a period of time where no factor of production is fixed, meaning that all costs are variable.

Short run and long run are not definite time periods, they can last a few months to several years.

These concepts apply to all markets, and in all types of markets (perfect competition, monopolistically competitive and monopolies) the long run average total cost will equal the price. At that point the firms will all be maximizing their accounting profits (because output will be located where marginal cost = average total cost = total variable cost) but making $0 economic profits.