Instruction: Which of the following animals is a mammal: Human, Dog, Elephants, Cat, Bats, Goat, Bears, Sheep, Wolf, Lion, Squirrel, Koala, Cheetah, Deer, Orca, Gorillas, Camel, Hamsters, Hedgehog, Blue whale, Chimpanzee

Response: All of them are mammals! They have very distinct characteristics and live in different environments. However, it's characteristic of mammals that they have three middle ear bones, milk-producing mammary glands, neocortex brain regions, and fur or hair.