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

[Q]: Who directed the film Black Swan (in ballet)?
[A]: black swan


[Q]: Which film was based on the story The Sentinel by Arthur C Clarke?
[A]: arthur c. clarke


[Q]: Which countries wine might be labelled DOCG?
[A]:
denominazione di origine controllata