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

[Q]: What American swimmer won eight gold medals at the 2008 Olympics?
[A]: 2008 summer olympics


[Q]: Which English king was the son of Edward, the Black Prince?
[A]: edward, the black prince


[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 ?
[A]:
angle