Karl Spent a Morning Evaluating His Production Staff and Recorded

Karl spent a morning evaluating his production staff and recorded their movements with a stopwatch. He realized he could reduce the distance workers walked to complete a process by simply changing the direction of flow of the product. Which element of Frank and Lillian Gilbreth's work is this an example of?

A) They used motion studies to eliminate unnecessary or repetitive motions from work. 
B) They proved the effectiveness of nonfinancial motivators in convincing workers to strive for organizational goals. 
C) They realized how the principles of sociology applied to worker performance. 
D) They identified the four functions managers perform.