Dennis Has Disorganized Type of Schizophrenia

Dennis has disorganized type of schizophrenia. He has lived in an institution for years. He rarely shows any attempt at socializing. A new program is started: every time Dennis speaks to another person he is given a piece of red paper. At the end of each week, he can use the red papers to get cigarettes or extra privileges. This new program is

A) guided exposure.
B) an in vivo exposure program.
C) a token economy.
D) modeling.