The best choice from the listed options 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 human pelvis does have vestigial aspects compared to those of other animals (like whales), it still plays a vital role in supporting the upper body and connecting to the lower body, making it functional. The other options describe structures that are largely vestigial in humans.