The correct option is C Hindlimbs
Vestigial structures are those that have lost some or all of their ancestral functions in a given species and yet, have been retained during the process of evolution. Such structures may however, be smaller/simpler in appearance than the typical structure. Hindlimb is a posterior appendage such as a leg or an equivalent (homologous) structure in other animals. Certain snakes such as pythons and boa constrictors have tiny hind leg bones buried in muscles toward their tail ends. This is also evidence that snakes descended from lizards during the course of evolution.