What Roles or Jobs Did African Americans Generally Hold in the Radio

What roles or jobs did African Americans generally hold in the radio industry?

A) Blacks were often staff musicians because they were heard and not seen.
B) African Americans did much of the writing, acting, and directing for the show Amos 'n' Andy.
C) Blacks were completely excluded from the entertainment industry during the 1930s and 1940s.
D) Radio stations refused to hire any blacks as disc jockeys.