Final answer:
The principle of animation for natural movement of a character's arms while walking is Follow Through and Overlapping Action, capturing how secondary parts move at different rates than primary motion.
Step-by-step explanation:
The principle of animation used to animate the movements of the character's arms while walking is known as Follow Through and Overlapping Action. This principle helps to create more natural movement by considering how different parts of a body move at different rates. For example, when a character walks, their arms swing in response to their steps to maintain balance, and the motion of the hands lags slightly behind the movement of the arms, exhibiting follow-through. The overlapping action refers to the secondary movements that follow the primary action, resulting in a more fluid and realistic portrayal of the character's locomotion.