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

Q: What is the country of origin of the cheese called caerphilly?

A: caerphilly cheese
****
Q: In which classic T.V. crime series did Captain Frank Furillo appear ?

A: frank furillo
****
Q: Which river flows from northern Moscow to the Caspian Sea?

A:
caspian sea
****