What is the single unique characteristic that distinguishes extant birds from other extant vertebrates?
A) endothermy
B) feathers
C) an amniotic egg
D) flight
E) a four-chambered heart

Question

Quizplus · Accepted Answer

Feathers are the single unique characteristic that distinguishes extant birds from other extant vertebrates. While other choices may apply to some birds, they are also found in other vertebrates. Feathers, on the other hand, are exclusive to birds.

What Is the Single Unique Characteristic That Distinguishes Extant Birds