Final answer:
Urban blues bands included the guitar, drums, and bass in their rhythm section, providing a foundation for the musical style that developed among African American musicians after World War I.
Step-by-step explanation:
African American musicians who trained in country blues and moved from the rural South to large northern cities after World War I developed the urban blues style. This new style reflected their life experiences and incorporated a variety of musical influences. The rhythm section of most urban blues bands typically included instruments such as the guitar, drums, and bass. These instruments provided a solid foundation for the music and supported the vocal lines and melodies that characterized the urban blues sound.