At a Given Level of Labor Employment, Knowing the Difference

At a given level of labor employment, knowing the difference between the average product of labor and the marginal product of labor tells you:

A) whether increasing labor use raises output.
B) whether increasing labor use changes the marginal product of labor.
C) whether economies of scale exist.
D) whether the law of diminishing returns applies.
E) how increasing labor use alters the average product of labor.