Answer:
B) equals the market price in perfect competition.
Step-by-step explanation:
Marginal revenue can be defined as the amount of money (revenue) generated from the sales of an additional unit of a product.
In a perfectly competitive market in long-run equilibrium, a long-run equilibrium avails firms the opportunity to adjust all inputs and all fixed costs are maximized. Also, it's characterized by free entry and exit, as such there isn't a fixed number of firms. This simply means that, since the number of firms in a long-run equilibrium can change, a firm must exit the market as a result of losses i.e when the firm is unable to cover its fixed costs in the long-run while new firms are allowed entry into the market when it anticipates potential profits or gains.
Hence, marginal revenue equals the market price in perfect competition.