Which function best describes the use of Onion Skinning within the animation process?

The use of Onion Skinning in the animation process primarily focuses on visually checking frame transitions. This technique allows animators to see several frames at once, typically the current frame and the frames immediately before and after it. By using Onion Skinning, an animator can evaluate the movement and timing of the characters or objects across frames, ensuring that transitions are smooth and maintain continuity in the animation. This visual reference aids in making precise adjustments to the artwork, which is essential for creating fluid motion and enhancing the overall quality of the animation.

The other options do not align with the primary function of Onion Skinning. For instance, sound design involves auditory elements, which Onion Skinning does not encompass. Creating annotations is more about documenting the animation process rather than facilitating visual transitions. Exporting scenes relates to finalizing and sharing the completed animation, which also falls outside the functions of Onion Skinning.