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

Q: Which English classic horse race for 3 year olds held at Doncaster every September began in 1776?

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

A: carl xvi gustaf of sweden
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Q: King Bhumibol Adulyadej, the 9th king of the House of Chakri, became the longest reigning current monarch in the world during his reign of which country from 1946?

A:
bhumibol adulyadej
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