Answer: The correct answer is letter "C": reinforcement theory.
Explanation:
By applying operant conditioning principles, a behavior can be modified if it's replaced by a positive or negative reinforcement. This approach was first studied and explored by the psychologist Edward Thorndike in 1911. This type of reward system functions by adding a favorable stimulus for the individual, called positive reinforcement. On the other hand, if an unfavorable stimulus is taken away, it's known as negative reinforcement.
