Given a factoid/trivia type question, generate the topic of the question. The topic is the entity the question talks about.
Q: What is the title of the 1866 operetta that Sullivan composed without Gilbert to a libretto by F C Burnand?
A:

Show your work and conclude with the exact phrasing "Therefore, the final answer is [answer]." where [answer] is just the final number or expression that solves the problem.
user
arthur sullivan