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: Dora Maar au Chat and The Weeping Woman are both portraits by which artist of his lover?

Answer: dora maar au chat


Question: What was the first Apollo mission to leave Earth orbit and orbit the moon, in 1968?

Answer: apollo


Question: Which singer and actress first performed the role of Christine in Phantom of the Opera in the West End in 1986?

Answer:
christine