Which of the following statements about operant learning is true?

Which of the following statements about operant learning is true?
 
  a. Operant learning or learning by rewards may explain how people operate in the workplace but it doesn't really explain how learning occurs in college classrooms.
  b. Operant learning maintains that people learn primarily by observing what others do.
  c. Although operant learning produces many consequences of behavior the most common are the positive or rewarding consequences and coercive or negative consequences.
  d. Operant learning maintains that the real or anticipated consequences of behavior can change the probability of that behavior's occurrence.
  e. None of the above