Which example best illustrates positive reinforcement?

The scenario involving giving a student a cookie for completing homework exemplifies positive reinforcement effectively. Positive reinforcement occurs when a desirable stimulus is presented following a behavior, which increases the likelihood of that behavior being repeated in the future. In this case, the cookie acts as a reward for the student’s effort and achievement in completing homework, encouraging them to continue this behavior.

This aligns with the principles of positive reinforcement, as the introduction of a pleasurable consequence (the cookie) reinforces the desired behavior (doing homework). The other scenarios involve either the removal of negative stimuli or consequences, which pertain to negative reinforcement or punishment rather than positive reinforcement.