Given a factoid/trivia type question, generate the topic of the question. The topic is the entity the question talks about.
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Question: Which group of the 1970's featured Tony Iommi on guitar, Geezer Butler on bass and Bill Ward on drums?

Answer: geezer butler


Question: In which war did the Sack of Badajoz takeplace?

Answer: siege of badajoz


Question: Who wrote the novella A Clockwork Orange?

Answer:
a clockwork orange