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

What is the nationality of Chelsy Davy, former girlfriend of Prince Harry?
chelsy davy

The Battle of Antietam was fought during which war?
battle of antietam

The 1994 Triptych Three Studies for Figures at the Base of Crucifixion was a breakthrough work by whom?

crucifixion