Final answer:
Mr. Slade's success likely refers to professional commercial theatre, which points to either Broadway or Off-Broadway theatres in New York as the places where he made it big.
Step-by-step explanation:
The question about where Mr. Slade made it big refers to a context of commercial theatre, which can be associated with different areas known for specific types of professional success. In New York, there are two main types of commercial theatre: Broadway and Off-Broadway. Broadway theatres seat more than 500 people and are renowned for their large-scale, high-budget productions, while Off-Broadway theatres seat between 100 and 499 people and can offer more experimental or intimate shows. As for Mr. Slade making it big, if it refers to commercial theatre success, the likely answers would be A) Broadway or B) Off-Broadway. Options C) Hollywood and D) Wall Street are associated with the film industry and financial sector, respectively, and are not typically related to a theatrical context.