Concept: Poultry keeping systems are classified by how birds are housed and managed. Intensive systems keep birds confined in a controlled environment.Explanation:The deep litter system keeps birds confined indoors in a house with a floor covered with litter material. It is a common example of an intensive system because the birds depend entirely on the farmer for feed, water, and care. Free range, free-running, and fold unit systems allow birds to move outdoors and are not classified as intensive.Answer:A. deep litter system.