Answer:
some animals exhibit structures that are no longer used for any purpose
Explanation:
Vestigial structures are defined as the the organs which are no longer used for any purpose.
Vestigial structures provide evidences of common ancestors as they shows how organisms changed or evolved in the use of these structures. for example: human appendix which is no longer functional in human body but as per Darwin's theory of evolution it was once used by our herbivorous ancestors to protect good bacteria in the gut.
Hence, the correct answer is "some animals exhibit structures that are no longer used for any purpose".
