Final answer:
Stratospheric phylogeny assumes C.convergence was common, indicating that similar traits in different species may evolve due to environmental pressures rather than from a recent common ancestor.
Step-by-step explanation:
Stratospheric phylogeny assumes that there are cases where organisms evolved through convergence and appear closely related but are not. Essentially, this concept accepts that evolutionary processes can result in organisms that are similar in function or form due to similar environmental pressures, rather than due to a recent common ancestry. Therefore, the correct answer is C. convergence was common.
Convergence means that the traits seen in different species are similar because of similar selection forces rather than a shared ancestry. Examples of convergent evolution include the development of wings in both birds and bats, which share a common ancestor that did not have wings. Thus, the answer captures the essence of stratospheric phylogeny which acknowledges that similar traits can evolve independently in different lineages through the process of convergence.