Final answer:
The correct answer is A) Derived traits; ancestral traits, with derived traits being new evolutionary features not present in common ancestors, and ancestral traits being older features that are found in common ancestors and their descendants.
Step-by-step explanation:
Derived traits are features that have evolved in a lineage and are not found in the common ancestor of the group, making them newer and unique to certain organisms within a clade. Ancestral traits, on the other hand, are characteristics that were present in the common ancestor and are thus more primitive features that can be found in both the ancestor and its descendants.
Shared derived traits are particularly important in cladistics, which is a method used to classify organisms based on common ancestry, as shown in phylogenetic trees and cladograms. These traits provide evidence for evolutionary changes and help in reconstructing the evolutionary history. When determining evolutionary relatedness, scientists look at homologous traits, which have the same evolutionary origins, as opposed to analogous traits that arise due to convergent evolution but do not indicate a close evolutionary relationship.