Marginal Revenue Product Falls as More Labour Is Hired Because

Multiple Choice

Marginal revenue product falls as more labour is hired because

A) the price of the product must fall for a perfectly competitive firm to sell more.
B) the wage rate rises as more workers work more hours.
C) the marginal product of labour is negative as additional units of labour are hired.
D) the marginal product of labour falls as a result of the law of diminishing returns.