Known for breaking down boundaries between artistic mediums, had close working relationships with composer john cage and choreographer merce cunningham.

The correct answer is Robert Rauschenberg. 
He was an American artist who lived during the 20th and in the beginning of the 21st centuries and was known for his pop art style of creating. He was a famous painter and a sculptor, and was quite known for his fluid art which broke down many boundaries between artistic forms. 

The answer is a. dramatic movement

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