Final answer:
Mr. Herrera is using a token economy in his classroom, where students earn tokens for good behavior, redeemable for preferred activities.
Step-by-step explanation:
Mr. Herrera is employing a token economy in his classroom, which is choice 'D'. A token economy is a behavior modification system that uses token reinforcers which can be traded in for rewards or privileges. In this scenario, paper fish are used as tokens which the students earn for non-disruptive behavior during lessons. If they accumulate at least 10 fish by the end of the week, they are rewarded with the opportunity to participate in preferred activities. This system of reinforcements helps in modifying behavior by increasing desired behaviors through the use of secondary reinforcers, which in this case are the paper fish. Token economies have been shown to be effective in various educational settings to enhance both behavior and academic performance.