Final answer:
The class Mammalia contains animals that have hollow bones, are warm-blooded, produce amniotic eggs, and have mammary glands.
Step-by-step explanation:
The class Mammalia contains the only animals that have hollow bones. They are also warm-blooded, meaning they can regulate their own body temperature. Additionally, mammals produce amniotic eggs, which are eggs that have a protective membrane around them. Finally, mammals are characterized by having mammary glands that produce milk to nourish their young.
Learn more about Characteristics of mammals