Which of the Following Statements Is True

Which of the following statements is true?

A) The average product of labour is at its maximum when the average product of labour equals the marginal product of labour.
B) The average product of labour is at its minimum when the average product of labour equals the marginal product of labour.
C) The average product of labour tells us how much output changes as the quantity of workers hired changes.
D) Whenever the marginal product of labour is greater than the average product of labour the average product of labour must be decreasing.