Crocodiles, bats, whales, and birds have similar limb bones. What do these similarities suggest?
A. Bats and crocodiles share an ancestor with whales but not with birds.
B. Crocodiles, bats, whales, and birds evolved from a common ancestor.
C. The common ancestor of birds and crocodiles was a whale.
D. A similar limb structure evolved in each species independently and by chance.