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

Example Input: Ageusia is the loss of which sense?
Example Output: ageusia

Example Input: Physics. What is the SI unit for amount of substance?
Example Output: amount of substance

Example Input: Which `Ian` featured on the Madness song `Drip Fed Fred`?
Example Output:
drip fed fred