Within the chordate classes, the unique characteristic of the class Aves is:

A) flight.
B) production of uric acid.
C) feathers.
D) endothermy.
E) a forked tongue.

Uric Acid

(uric acid) The principal nitrogenous excretory product of insects, birds, and reptiles; a relatively insoluble end product of protein metabolism; also occurs in mammals as an end product of purine metabolism.

Endothermy

The physiological capability of an organism to maintain a stable internal body temperature regardless of external environmental conditions.

Aves

A class within the animal kingdom that encompasses all birds, characterized by feathers, beak with no teeth, and the laying of hard-shelled eggs.