Answer:
positive reinforcement ( D )
Step-by-step explanation:
The red cross thanking its volunteers with public recognition for their good works towards the cause of the Red cross will motivate or encourage positive response/behavior of the volunteers in the future when called upon for their service again. this type of encouragement towards the volunteers is known as what we call positive reinforcement.
piece-rate scaling is a production type of scaling that is used to reward workers based on their individual output i.e paying them based on how productive they are. this is applicable to a profit based organization and not a not-for-profit organization like Red cross society.