Which of the following statements is true about marginal cost of production?

A. The marginal cost curve is U-shaped

B. Marginal cost is the extra cost of producing one additional unit of output.

C. Marginal cost will be rising if the marginal product of a variable resource is falling (diminishing returns are being experienced).

D. Marginal cost equals the change in total costs divided by the change in the output level

E. All of the above