Species X and species Y are living animal species that have many similar physical characteristics. These characteristics suggest the species are closely related.

Which of the following would be the best evidence that species X and species Y have a common ancestor?
A.
A fossil of a different species is found that has some of the characteristics shared by species X and species Y.

B.
A fossil of a different species is found that has none of the characteristics shared by species X and species Y.

C.
A third living species is found that has none of the characteristics shared by species X and species Y.

D.
A third living species is found that has some of the characteristics shared by species X and species Y.