Which type of symbol adds less to the FLA file size due to the absence of its timeline?

The graphic symbol is the correct choice because it does not have its own timeline, which is a significant factor in determining the overall file size of the FLA. Graphic symbols are designed to be lightweight; they are simple representations of graphics that can be reused throughout the project. Since they do not carry their own timeline, they do not include the additional data associated with frame-based animations, reducing the overall FLA file size.

In contrast, movie clip symbols and button symbols each contain their own timelines and interactivity features, which adds complexity and size to the file. Movie clips often feature animations and events that can increase file size, while button symbols require additional properties and states that also contribute to more data. As for layer symbols, this category does not actually exist within Adobe Animate as a distinct type of symbol, further distinguishing graphic symbols as the ideal choice in this context.