Which of the following is considered a primary reinforcer?

The choice of food for satisfying hunger is considered a primary reinforcer because it directly fulfills a basic biological need. Primary reinforcers are stimuli that are naturally reinforcing due to their intrinsic value to the individual. In the case of food, it is essential for survival and is universally recognized as a powerful motivator for behavior, particularly in terms of reinforcement and conditioning.

Other options, while they may serve as reinforcers, do not fulfill a fundamental biological necessity. Tangible rewards like tokens and praise for good behavior are secondary reinforcers, which gain their reinforcing properties through association with primary reinforcers. A comfortable chair, although it may provide physical comfort, is also not a primary reinforcer since it does not directly address a biological need like hunger does. Thus, food stands out as the most direct and necessary form of reinforcement in this context.