Answer: Option (d) is correct.
Explanation:
Correct option: Raise output until marginal costs are equal to marginal revenue.
When the firm is profit maximizing and operates in a competitive environment, it should raise output until the point where marginal costs of firm is equal to the marginal revenue if marginal costs are falling.
As this will cover firm's more costs from producing more output. At a point where the marginal cost is equal to the marginal revenue, firm is maximizing its profit.