Answer:
Musical structure.
Explanation:
The A represents a musical idea or ideas, the B represents new, contrasting material, and the final A represents a return to the familiar music heard in the opening of the piece.
Contrast: The work in today's art is a lot more advanced. Prehistoric people were simple and didn't use the major fundamentals of art. They're work is really abstract and really only consisted of warm colors and black.
Compare: Like some of today's artists, some of the prehistoric painting tell stories, or describe ones feelings.
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