The odd one out is A. Kangaroo. The other three options are all primates, while kangaroos are marsupials.
A kangaroo is a large, leaping marsupial mammal native to Australia. It has a long, muscular tail and large hind legs, which it uses for jumping. Kangaroos are herbivores and eat mostly grasses, leaves, and fruits. They live in herds and are social animals.
An orangutan is a large, arboreal ape native to the rainforests of Indonesia and Malaysia. It has a long, reddish-brown coat and a large head with a prominent brow ridge. Orangutans are solitary animals and spend most of their time in trees. They are herbivores and eat mostly fruit, leaves, and insects.
A gorilla is a large, powerful ape native to Africa. It has a long, black coat and a large head with a prominent brow ridge. Gorillas are herbivores and eat mostly leaves, shoots, and fruits. They live in groups and are social animals.
A baboon is a large, monkey-like ape native to Africa. It has a long, dog-like snout and a large head with a prominent brow ridge. Baboons are omnivores and eat mostly fruit, insects, and small mammals. They live in groups and are social animals.