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

[Q]: The Battle of Antietam was fought during which war?
[A]: battle of antietam


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


[Q]: Who played 'Harvey 'Big Daddy' Pollitt' in the 1958 film 'Cat On A Hot Tin Roof'?
[A]:
cat on a hot tin roof