When Labor Is the Only Input to the Production Function

Multiple Choice

When labor is the only input to the production function, why must it be true that when the marginal product of labor is greater than the average product of labor, the average product of labor is increasing and vice versa?

A) When the marginal product of labor is above the average product of labor, an additional unit of labor will produce a greater marginal product than average, thus raising the average.
B) When the marginal product of labor is below the average product of labor, an additional unit of labor will produce a greater marginal product than average, thus raising the average.
C) When the marginal product of labor is above the average product of labor, an additional unit of labor will produce a smaller marginal product than average, thus reducing the average.
D) When the marginal product of labor is above the average product of labor, an additional unit of labor will produce a zero marginal product.