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: Princess Estelle, Duchess of Ostergotland, granddaughter to King Carl XVI Gustaf, became 2nd in line to what nation's throne when born in 2012?

Answer: carl xvi gustaf of sweden


Question: Who has written a series of novels, entitled The Dark Tower, of which the first, in 1982, was entitled, The Gunslinger?

Answer: the dark tower


Question: In which Shakespeare play does the character Antigonus exit, pursued by a bear?

Answer:
antigonus