I believe the correct answer is B. writing sheet music.
A is definitely not correct because it was a different time, and concerts were not as popular as today's are, and even if they were, they wouldn't bring that much money to the artists. C is also incorrect because how rich can you get if you sell a couple of instruments? Although D was a popular 'job' at the time, it didn't bring nearly as much money as writing sheet music to be performed elsewhere.
