the answer is:D. Rewarding a child for finishing his oatmeal mush and counting how many times the child needs to be rewarded before he finishes his oatmeal voluntarily
In operant conditioning , we try to enforce a certain type of habit or behaviors to the subjects by utilizing the use of rewards (when the subjects show a desired behavior) or punishment (when the subjects fail to show the desired behavior).
Option D fulfill this criteria, The Enforced habit would be Finishing his oatmeal voluntarily and they utilize the use of rewards every time the child finish his oatmeal mush in order to enforce it.