The correct answer is: Albert has a beautiful garden in his backyard and notices that hummingbirds feed on the flowers at the same time each day in order to get the most nectar. The hummingbirds are being rewarded for their feeding behavior on an fixed interval schedule of reinforcement.
A fixed interval schedule is a type of reinforcement where after the individual makes the first response, is only rewarded after a specific amount of time has passed. This type of reinforcement is done to generate in the individual an association between the action of doing certain behavior and the consequence that this last one brings.