The Marginal Product of Capital

The marginal product of capital:

A) is equal to the increase in capital necessary to generate a one-unit increase in output.
B) is equal to the increase in output obtained from a one-unit increase in capital, holding other factors constant.
C) is equal to the incremental profit associated with selling one more unit of output.
D) is equal to the incremental cost of employing one more unit of physical or human capital.