Final answer:
Positive reinforcement involves adding a positive stimulus to increase a behavior, which matches option A. adding something positive, increases from the provided choices.
Step-by-step explanation:
According to Stimulus Response theory, positive reinforcement involves adding something positive and has been shown to increase behavior. The correct answer to the student's question is therefore A. adding something positive, increases. Reinforcement, specifically positive reinforcement, includes adding a desirable stimulus to a situation to encourage a behavior. This can make it more likely that the behavior will occur again in the future. This is distinct from negative reinforcement, which involves removing an undesirable stimulus to increase a behavior, and punishment, which always aims to decrease a behavior.