Which of the following is a method used in differential reinforcement?

The correct answer is the Differential Reinforcement of Other behaviors (DRO), as it specifically refers to a strategy within the broader framework of differential reinforcement. DRO focuses on reinforcing an individual for not engaging in a challenging behavior during a specified time period. This method effectively reduces undesirable behaviors by providing reinforcement for the absence of those behaviors, promoting more adaptive or alternative behaviors.

While positive reinforcement is indeed a fundamental behavior modification technique, it can be employed in various contexts, not exclusively linked to differential reinforcement. Negative punishment and time-out procedures address a decrease in unwanted behaviors but do not align specifically with the differential reinforcement approach. DRO stands out as it directly emphasizes the reinforcement of time periods where the undesired behavior is absent, making it the most fitting answer in the context of the question.