The Law of Diminishing Marginal Returns States

The law of diminishing marginal returns states

A) that at some point, adding more of a fixed input to a given amount of variable inputs will cause the marginal product of the variable input to decline.
B) that at some point, adding more of a variable input to a given amount of a fixed input will cause the marginal product of the variable input to decline.
C) that in the presence of a fixed factor, at some point average product of labour starts to fall as more and more variable inputs are added.
D) that average total costs of production initially fall and after some point start to rise at a decreasing rate as output increases.