instruction:
Given a factoid/trivia type question, generate the topic of the question. The topic is the entity the question talks about.
question:
What currency is used on Christmas Island?
answer:
christmas island


question:
Which instrument was Benny Goodman famous for playing?
answer:
benny goodman


question:
Who directed the 1942 film, 'Casablanca'?
answer:

casablanca