The correct answers are, 1.- Operetta, 3.- Vaudeville, 4.- Ragtime.
The genres that historians believe helped to pave the way for the Broadway musical are Operetta, Vaudeville, and Ragtime.
One of the first formal musical son Broadway was The Show Boat, in 1927. There are some genres that influenced musicals such as Operetta, the Revue, the Burlesque, musical comedies, and extravaganzas. The characteristics of a Broadway musical is that it comprises music, singing, dancing, a story.