How Did the Nation's Regional and Cultural Geography Shape the American

How did the nation's regional and cultural geography shape the American music and radio industries during the 1920s?

A) Record companies discovered lucrative regional and ethnic music markets, such as country music and jazz, that gained popularity with both national and foreign listeners due to radio transmissions.
B) Mexican radio stations close to the American border popularized Spanish music and language broadcasts throughout the United States.
C) Ethnic music and foreign language shows that had been played on smaller, independent radio stations continued to be broadcast and remained popular on a nationwide basis when these stations were taken over by larger radio networks.
D) The appeal of "hillbilly" and "race" music was limited to their distinctive geographic regions and failed to transcend to listening audiences in other parts of the United States.