The option that is not a reason that author Carl Engel gives for Jazz's popularity is option C. Jazz follows a strict tradition and morality.
Carl Engel was a French-born American pianist, musicologist and publisher from Paris. He was also a writer on music for The Musical Quarterly, and chief of the Music Division of the Library of Congress.
He was the writer of: JAZZ: A MUSICAL DISCUSSION" In that he claimed: Good jazz is the latest phase of American popular music.