Question

it can be seen on a cladogram that modern birds and reptiles share a common ancestor. select the piece of evidence that best supports this idea.
reptiles are also related to mammals.
birds have evolved into many groups.
feathers are a derived characteristic that first evolved in reptiles.
birds have the derived characteristic of being warm blooded, like mammals.

Explanation:

Cladograms use shared derived characteristics to show evolutionary relationships. A trait originating in a common ancestor and passed to descendants supports shared ancestry. Feathers evolving first in reptiles (a derived trait) links birds (which have feathers) to reptiles via a common ancestor. Other options do not directly connect birds and reptiles through shared ancestry.

Answer:

Feathers are a derived characteristic that first evolved in reptiles.