The law of diminishing returns indicates that:a. because of economies and diseconomies of scale a competitive firm's long-run average total cost curve will be U-shaped.b. the demand for goods produced by purely competitive industries is downsloping.c. as extra units of a variable resource are added to a fixed resource, marginal product will decline beyond some point.d. beyond some point the extra utility derived from additional units of a product will yield the consumer smaller and smaller extra amounts of satisfaction.

The law of diminishing returns states that as we go on employing additional inputs the return or payoff from each unit of input will become smaller or go on declining. This means that after a certain point the total output will start increasing on a decreasing rate as we go on hiring more inputs.

In other words, the marginal product of inputs will go on declining with each additional unit of input employed. As a result after reaching a certain point, the marginal product starts to decline.