Final answer:
During the girl-group era in the 1960s, many of the hits were produced by songwriters based in the Brill Building and other songwriting hubs in New York City.
Step-by-step explanation:
The answer to the question is d) The Brill Building and other songwriting hubs in New York City.
During the girl-group era in the 1960s, many of the hits were produced by songwriters based in the Brill Building and other songwriting hubs in New York City. These songwriters, such as Carole King and Gerry Goffin, wrote popular songs for girl groups like The Shirelles and The Crystals. The Brill Building became synonymous with the production of many successful hits during this time.