Which feature is primarily used to assist in ensuring animation continuity?

Onion Skinning is a crucial feature in animation that allows animators to see multiple frames at once, both the current frame and surrounding frames. This transparency helps in maintaining animation continuity by providing a visual guide to the positions of characters and objects as they move, which aids in creating fluid transitions between poses or actions. By displaying previous and subsequent frames, onion skinning enables artists to align their movements more accurately, ensuring that the animation appears seamless and cohesive as it progresses from one frame to the next.

While other features also play important roles in the animation process, they do not specifically target continuity in the same way. Keyframes are essential for defining specific points of action, but they don’t show intermediate motion. Scene Properties provide contextual information about scenes but do not influence the animation's visual flow directly. Storyboard Templates assist in planning and structuring the visual story but don’t specifically help in adjusting the timing and continuity of movement between frames. Thus, the use of onion skinning is particularly vital for achieving smooth animation continuity.