A profit-maximizing firm will produce a level of output where:

marginal revenue is equal to marginal cost.Correct
price is equal to average cost.
price is greater than marginal revenue.
average cost is equal to marginal revenue.

Explanation
Firms will maximize profits or, in other words, make the most amount of profit, when the marginal cost of the last unit of output equals the marginal revenue, or MC = MR.