tephen Foster A. most important dancer of Fox-Trot in American popular music B. inventor of Rag Time C. most important song writer in nineteenth-century American popular music D. most important Big-Band leader in nineteenth-century American popular music

None of the above

Explanation:

Stephen Foster was an American singer-songwriter, but he wasn't the most important dancer, or song writer of the XIX century, the inventor of Rag Time or the most important Big-Band leader in nineteenth-century American popular music.