Answer:
They each have vestigial structures.
Explanation:
Birds and humans have a common ancestor as they have homologous structures.
Vestigial structures are the organs that have some important functions in the past but now in present, they do not perform any function.
Both humans and birds have vestigial structures such as humans have an appendix and ear pinna and wings of flightless birds such as ostrich.
Hence, the correct answer is "They each have vestigial structures.".
