Given a factoid/trivia type question, generate the topic of the question. The topic is the entity the question talks about.

Example Input: In which city could you visit the Anne Frank House?
Example Output: anne frank house

Example Input: What is the only nation state of the Commonwealth of Nations on the mainland of South America?
Example Output: commonwealth of nations

Example Input: Billund Airport is in which European country?
Example Output:
billund