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: According to the bible, Zaccariah was the father of which New Testament figure?

Answer: bible


Question: Which American actor and singer has joined Amanda Holden as one of the judges on the current series of 'Britain's Got Talent'?

Answer: britain's got talent


Question: In which European city is the Arch of Titus?

Answer:
arch of titus