Question

which statement about the evolution of mammals is true?
a mammals can only walk on land.
b mammals come from more than one common ancestor.
c all mammals have vestigial hind limbs.
d mammals’ limbs are homologous structures.

Explanation:

• Option a: Mammals like whales swim and bats fly, so they don't only walk on land. Incorrect.
• Option b: Mammals share a single common ancestor (the first mammal - like creature), so this is incorrect.
• Option c: Not all mammals have vestigial hind limbs (e.g., many terrestrial mammals use their hind limbs for movement, not vestigial). Incorrect.
• Option d: Mammals' limbs are homologous structures as they have a common evolutionary origin (from tetrapod ancestors) but may have different functions (e.g., human arms, bat wings, whale flippers), which fits the definition of homologous structures. Correct.

Answer:

d. Mammals’ limbs are homologous structures.