Answer:
1. mammary glands
2. vertebral column
3. four limbs
Step-by-step explanation:
Whales and humans have many more detailed features in common (homologies) than do whales and fish because whales and humans share a most recent common ancestor. Whales and humans are mammals (Class Mammalia), whereas fish are not mammals. First, both whales and humans have mammary glands: whales have mammary glands on the chest and stomach (like other mammals). Second, nearly all mammals have a vertebral column composed of 7 cervical vertebrae (humans and whales are not an exception to this rule). Like other mammals, whales have four limbs: although whales are adapted to live underwater, they evolved from a terrestrial mammal ancestor that once walked on four legs (about 50 million years ago).