What is the difference between a firm's marginal revenue and its marginal revenue product?

A) Marginal revenue is the change in sales revenue from selling one more unit of output while marginal revenue product is the change in total revenue from hiring one more worker.
B) There is no difference between the two terms.
C) Marginal revenue is the increase in revenue when a firm raises its output price while marginal revenue product is the increase in marginal product when a firm hires an additional worker.
D) Marginal revenue is the change in sales revenue from selling one more unit of output while marginal revenue product is the profit earned from hiring one more worker.

A