Answer:
M&Ms to make her feel better. The next time art class meets, Nadia promptly and purposefully spills water. The M&Ms acted as positive reinforces.
Step-by-step explanation:
According to the operant conditioning theory, positive reinforcement is the reward or stimulus which strengthens the likelihood of a particular behavior. Positive reinforcement is followed by a particular action so that the children would pair rewards with a particular behavior and it becomes repetitive in the future. As per the question, M&M chocolates would work as a reward and the behavior of Nadia would become repetitive.