In the opening movement of vivaldi’s "spring," which technique does he use to introduce contrast?

short staccato notes

ritornello

triple time

terraced dynamics 

I think the answer would be terraced dynamics. Terraced dynamics is a musical style characterized by abrupt volume shifts from soft to loud and back within a piece.

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artists need to create a realistic interpretation so that people in general can relate to the artwork. for a common people, an artist's impression gets increased only if he can create something which would look realistic. an abstract is difficult for a common people to understand whereas if a person can draw a girl with simple pencil sketch and if that looks like a real figure then the latter will be praised more than the former.