Final answer:
Positive reinforcement increases behavior, while positive punishment decreases behavior.
Step-by-step explanation:
In operant conditioning, positive reinforcement is when a desirable stimulus is added to increase a behavior, while positive punishment is when an undesirable stimulus is added to decrease a behavior.
For example, if you receive a reward for completing your homework (adding a desirable stimulus), you are more likely to continue completing your homework in the future. On the other hand, if you receive a detention for talking in class (adding an undesirable stimulus), you are less likely to talk in class in the future.
Therefore, the correct answer is option a) increase; decrease.