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.

photography had emerged as an elite art pursued by a few creative individuals for a few wealthy patrons. but now, said bauldelaire, it was succumbing to "the great industrial madness of our times." it was becoming a mass production industry that catered to middle-class tastes, including a taste for gadgetry. the stereoscope, the first 3d imaging system, had turned looking at photographs into parlor entertainment. a "thousand hungry eyes were bending over the peepholes of the stereoscope as though they were the attic-windows of the infinite.