What is a shared ancestral trait and how does it affect phylogeny?

What is a shared ancestral trait and how does it affect phylogeny?

• A. A trait present in the ancestor; it is uninformative for resolving relationships within a group
• B. A trait that evolved within a lineage and defines a clade
• C. A trait arising by convergent evolution
• D. A trait that is unique to an outgroup

Answer: (A)