Question

what is a vestigial structure?
a structure that no longer serves a function
a structure that is used by several organisms in different ways
a structure found in different organisms, but serves a similar function

Explanation:

A vestigial structure is a body part that has lost its original function through evolution. For example, the appendix in humans is considered vestigial as it no longer serves a significant digestive function like it may have in our ancestors.

Answer:

a structure that no longer serves a function