Which of the following would provide the best evidence that species a and species b have a common ancestor?   species a has limbs, and species b does not have limbs. the limbs of species a perform a function that is similar to the limbs of species b, but they have a different structure. the limbs of species a and species b have a different structure and function. the limbs of species a have a similar structure to the limbs of species b, but they perform a different function. es a and species b have a common ancestor?