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

[Q]: What is the main river of Brazil?
[A]: brazil


[Q]: In which English city was Damien Hirst born?
[A]: damien hirst


[Q]: Ian Gillan and David Coverdale have both provided lead vocals for 'Rock' group?
[A]:
david coverdale