The law of diminishing returns states that as
A.
the size of a plant increases, the firm's fixed cost decreases.
B.
the size of a plant increases, the firm's fixed cost increases.
C.
a firm uses more of a variable input, given the quantity of fixed inputs, the marginal product of the variable input eventually diminishes.
D.
a firm uses more of a variable input, given the quantity of fixed inputs, the firm's average total cost will decrease eventually.