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

Example Input: Cilantro is the leaf of which herb?
Example Output: cilantro

Example Input: In which US state are the Catskill Mountains?
Example Output: catskill mountains

Example Input: Which Welsh actor portrays David Frost in the 2008 film, Frost/Nixon?
Example Output:
frost/nixon