Anatomical features that are fully developed and functional in one group of organisms but reduced and functionless in a similar group are termed:
a. analogous.
b. homologous.
c. vestigial.
d. sympatric.
e. polygenic.

c. vestigial.

Explanation:

Vestigial organs are small, non-functional and often degenerate organs present in some living organisms. These organs are thought to have been completely developed and well functional in the ancestors of these organisms.

Vestigial organs are one of the morphological evidences used in the support of evolution. Example include caudal vertebrae, appendix and wisdom tooth in man.

The correct option is c.