Which of the Following Statements Is True

Multiple Choice

Which of the following statements is true ?

A) When marginal cost is below average cost, average cost rises; when marginal cost is above average cost, average cost falls.
B) The marginal product is the output per unit of a variable input.
C) Average variable cost and average fixed cost are U-shaped curves.
D) When marginal productivity of a variable input is falling then marginal costs of production must be rising.