The correct option that serves a purpose in humans is (pelvis: supports upper body and attaches to lower body in humans versus being tiny and nonfunctional in legless animals like whales and snakes).
While the other options mention structures which are considered vestigial and have lost their primary function in humans, the pelvis has an essential role in providing structural support and facilitating movement in our species.
The other structures you mentioned (tailbone, goosebumps, and ear muscles) are vestigial in humans, meaning they do not serve the same functional purpose they do in other animals.