In Mr. Medeiros classroom, students are given play money each time they turn in an assignment; they receive additional amounts of money if the assignment is turned in on time and if it is done correctly. At the end of each week, students can use their play money to purchase special privileges (free time, special privileges, etc.). Mr. Medeiros approach can best be characterized as:a. Intermittent reinforcement.b. A group contingency.c. A token economy.d. A contingency contract.