The correct answer is: A. Marginal revenue is greater than marginal cost.
A monopolist is the only seller of a good or service in a market. This means that they have a great deal of market power and can set their own prices. In order to maximize profit, a monopolist will produce and sell their output at the point where marginal revenue is equal to marginal cost.
Marginal revenue is the additional revenue that a firm earns from selling one more unit of output. Marginal cost is the additional cost that a firm incurs from producing one more unit of output. When marginal revenue is equal to marginal cost, the firm is producing at the point where the additional revenue from selling one more unit of output is equal to the additional cost of producing that unit. This is the point at which the firm is maximizing its profit.
Option B is incorrect because marginal revenue and marginal cost are equal at the point of profit maximization. Option C is incorrect because marginal cost is greater than marginal revenue at all points below the point of profit maximization. Option D is incorrect because marginal revenue is always equal to average revenue at the point of profit maximization.