Which of the Following Correctly Defines Marginal Cost

Multiple Choice

Which of the following correctly defines marginal cost?

A) Marginal cost is the addition made to fixed cost when an extra unit is produced.
B) Marginal cost is the additional cost of producing an extra unit of output.
C) Marginal cost is the additional cost of increasing the scale of production in the long run.
D) Marginal cost is the difference between price and marginal revenue for the last unit sold.
E) Marginal cost is the same as the firm's variable cost at all levels of output.