Final answer:
An animal with vertebrae, dorsal hollow nerve cord, hair, and mammary glands is a mammal. This class of endothermic vertebrates has a backbone, breathes with lungs, has hair or fur, and females produce milk for the offspring.
Step-by-step explanation:
An animal characterized by having vertebrae, a dorsal hollow nerve cord, hair, and mammary glands must be a mammal. Mammals are a class of endothermic vertebrates known for their distinctive characteristics, such as having a bony endoskeleton with a backbone, breathing with lungs, and having four limbs. Their skin is covered with hair or fur, and their reproductive strategy includes producing amniotic eggs. Furthermore, the presence of mammary glands in females, which produce milk for newborns, is a defining feature of mammals.
The mammalian class includes various clades like monotremes, marsupials, and eutherians (or placental mammals). Mammals also exhibit other traits like the presence of sweat glands, alveoli in the lungs for efficient gas exchange, a four-chambered heart for effective circulation of blood, and a complex brain with a neocortex covering. Therefore, the animal described with the listed features is unequivocally categorized as a mammal.