Which of the Following Provides an Explanation of How a Differential

Which of the following provides an explanation of how a differential piece-rate system pays employees?

A) one piece-rate wage for standard production, but less if producing below quota
B) one piece-rate wage for units produced up to a standard output and a higher piece-rate wage for units produced over the standard
C) differential wages depending on the differing responsibilities in the production of each unit
D) a higher rate per piece for employees with more experience and seniority