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

[EX Q]: In which opera does a hunchback jester help his master, the Duke of Mantua, to seduce the daughter of a courtier?
[EX A]: duke of mantua

[EX Q]: On November 22, 1986, which boxer became the youngest WBC Heavyweight champion, at age 20 years, 4 months, when he scored a TKO over Trevor Berbick in the second round?
[EX A]: boxing

[EX Q]: Which golfer won the 2011 US Open?
[EX A]:
2011 u.s. open