The Law of Diminishing Returns Indicates Why

The law of diminishing returns indicates why

A) beyond some point, the extra utility derived from additional units of a product will yield the consumer smaller and smaller amounts of additional satisfaction.
B) the firm's total fixed costs do not change with output in the short run.
C) a firm's long-run average total cost curve is U-shaped.
D) a firm's marginal costs will eventually increase as the firm expands output in the short run.