单选题 Holding the quantity of labor constant, output increases as the quantity of capital increases, but at a decreasing rate. This phenomenon is most accurately described as: A. diminishing marginal costs of capital. B. diminishing marginal returns to labor. C. diminishing marginal product of capital.

【正确答案】 C

【答案解析】The marginal product of capital is the change in output divided by a unit change in capital, holding labor constant. Diminishing marginal product of capital means that at a constant level of labor, output increases as capital is added, but at a decreasing rate.