Was one of the most lucrative parts of the music business at the end of the nineteenth century.
a. giving concerts
b. writing sheet music
c. selling instruments
d. providing music lessons

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. 

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