18. Why did so many African-American leaders reject Marcus Garvey?19. How did the black nationalism of the Universal Negro Improvement Association differ from the white nationalism of the Ku Klux Klan? 20. What economic opportunities existed for African Americans who had migrated to northern cities? 21. How do you explain the emergence of the literary and artistic movement known as the Harlem Renaissance? 22. How distinctive were black writers, artists, and musicians? Were their creative works essentially a part of American culture or separate from it? 23. Were there any genuine reasons for optimism among African Americans by the late 1920s?