The Thick Thigh and Skinny Lower Leg of a Bird,as

The thick thigh and skinny lower leg of a bird,as in the case of a chicken leg,is an advantage because it

A) loads the muscle mass near the body's center of gravity for flight.
B) only leaves bone, tendon and tough skin exposed to freezing conditions.
C) keeps the slender, lightweight feet from being muscle-bound and restricted.
D) All of the choices are advantages
E) None of the choices are correct