instruction:
Given a factoid/trivia type question, generate the topic of the question. The topic is the entity the question talks about.
question:
Brasilia is the capital but which city in Brazil has the largest population?
answer:
brazil


question:
Ride of the Valkyries is the official quick march of which branch of the British Army?
answer:
british army


question:
Which instrument is most closely associated with jazz musician Charlie Mingus?
answer:

charles mingus