Final answer:
The statement about John Gay's The Beggar's Opera using popular music ballads of the time is true, emphasizing the work's place within the evolution of musical theatre, reflecting societal trends and cultural shifts.
Step-by-step explanation:
John Gay's The Beggar's Opera indeed makes use of ballads from the popular music of his day. The assertion about The Beggar's Opera is true. This work is an example of a ballad opera, a genre that integrates songs known to the audience into its narrative structure. Gay's opera was revolutionary in part because it included melodies and lyrics from popular music of the time, making it accessible and immediately familiar to its audience.
The evolution of musical theatre reflects significant cultural and economical transformations. The market revolution did indeed bring about many social and economic changes to the United States, which is true. Musicals like Guys and Dolls and West Side Story from the 1950s exemplified these changes in culture and society, bringing the art form to new heights of popularity. The continuous evolution of the musical theatre genre demonstrates the way societal trends and tastes shape the arts.