Final answer:
Henry Purcell's 'Dido and Aeneas' libretto was written in English, making it one of the pioneering operas in the English language during a time of rich theatrical and musical culture.
Step-by-step explanation:
The libretto of Henry Purcell's Dido and Aeneas was originally written in English, making it one of the first operas in this language. It capitalized on the rising trend of music and theatrical works that were prevalent during the late Renaissance period.
Opera emerged as a genre in Florence as an attempt to resurrect the music of ancient Greece, and it soon became an integral part of European high culture. By the time of Henry Purcell, the fusion of dramatic narrative with musical score had become highly refined.