Skinner's theory of operational conditioning is a fundamental part of the principle of reinforcement. Skinner refers to all events that increase the probability of an individual's operational response in the conditional action. He distinguishes between two types Reinforcement: positive reinforcement and negative reinforcement. When a certain stimulus in the environment increases and the probability of behavioral response increases, the increase in this stimulus is positive reinforcement; when a certain stimulus in the environment decreases and the probability of behavioral response increases, This reduction in stimulation is negative reinforcement. Which of the following are not positive reinforcements. ['Teachers praise students who observe discipline in class.', 'Parents give material encouragement to children with good test results.', 'The school dismisses a student whose behavior has improved.', 'Company bosses increase salary for hard-working employees.']