At Plains High School, students who are tardy to class are given "Yard Patrol" after school. Yard patrol amounts to requiring the students to clean up any trash found on the school grounds. As it turns out, the strategy is moderately successful; fewer students are tardy to class. Which of the following concepts from operant conditioning is best illustrated by the school's strategy? 

a. Negative reinforcement 

b. Presentation punishment 

c. Satiation 

d. Extinction