Final answer:
The answer to which concept is not a reason for engaging in prosocial behavior is d. 'positive-state relief'; other motivations for prosocial behavior include empathic joy, negative-state relief, competitive altruism, and reciprocal altruism.
Step-by-step explanation:
The concept that is not one of the reasons why people engage in prosocial behavior is positive-state relief. Prosocial behavior, such as altruism, involves voluntary behavior with the intent to help other people. This could be rooted in various motivations, including empathic joy (the pleasure from seeing others benefit), negative-state relief (the reduction of one's own distress by helping others), competitive altruism (helping others to boost one's own reputation or status), and reciprocal altruism (helping others with the expectation that they will help in return). Positive-state relief does not correspond with the altruistic motivations detailed in the studies of prosocial behavior and is therefore not a concept typically associated with the reasons why people help others.