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 US state are the Catskill Mountains?
[EX A]: catskill mountains

[EX Q]: Which instrument was Benny Goodman famous for playing?
[EX A]: benny goodman

[EX Q]: In geometry, which unit is defined as being equal to the angle subtended at the centre of a circle by an arc equal in length to the radius ?
[EX A]:
angle