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

[Q]: Who wrote the novel 'Brideshead Revisited'?
[A]: brideshead revisited


[Q]: On which island is Nassau, the capital of the Bahamas?
[A]: nassau


[Q]: Which 'Dr. Who' actor came between Patrick Troughton and Tom Baker?
[A]:
dr. who