The Law of Decreasing Returns States That as a Firm

The law of decreasing returns states that as a firm uses more of a

A) fixed input, with a given quantity of variable inputs, the marginal product of the fixed input eventually decreases.
B) variable input, total output will increase indefinitely.
C) variable input, with a given quantity of fixed inputs, the marginal product of the variable input eventually decreases.
D) variable input, output will begin to fall immediately.
E) fixed input and a variable input, the marginal product of the fixed input and the marginal product of the variable input both decrease.