Final answer:
The prevalent form of opera during the Classical era known for its virtuosic recitatives and arias was called opera seria. This style was serious in tone, often with heroic themes from history or mythology, and popular in the 18th century, especially in Italian and German-speaking regions.
Step-by-step explanation:
The prevalent form of opera during the Classical era, which was known for its many recitatives and arias that showcased the performers' virtuosity, was called opera seria. Unlike opera buffa, Singspiel, or opéra comique, which each had their own distinct characteristics, opera seria was a serious form of opera that typically had lofty, heroic themes, often derived from history or mythology. This style of opera was immensely popular throughout the 18th century, particularly in Italian and German-speaking countries, which held many such performances in their ornate opera houses.