Question

the table shows key features of hippos, ambulocetus, and whales.
feature hippos ambulocetus whales
pelvic bones large and functional functional but smaller vestigial (no function)
limbs legs for walking webbed feet (walking and swimming) flippers (swimming only)
how do the vestigial pelvic bones of whales suggest they came from land mammals?
they show that whales evolved from reptile - like ancestors with strong fins.
they help whales move their tails and balance their large bodies.
they prove that whales once lived on land before adapting to water.
they show that whales had ancestors with functional legs for walking.

Explanation:

Vestigial structures are remnants of organs or structures that were functional in ancestors. Whales having vestigial pelvic bones implies their ancestors had functional legs for walking as pelvic bones are related to leg - attachment in land - dwelling animals.

Answer:

They show that whales had ancestors with functional legs for walking.