A four-chambered heart with a right systemic arch is present in Birds

Birds have a unique circulatory system in which they possess a four-chambered heart with complete separation of oxygenated (left side) and deoxygenated (right side) blood, but they have a right systemic arch. This adaptation allows them to meet the high oxygen demands of their active lifestyles, such as flying. Mammals (Option D) also have a four-chambered heart, but they typically have a left systemic arch. Amphibians (Option A) and reptiles (Option B) generally have three-chambered hearts with varying degrees of mixing of oxygenated and deoxygenated blood.