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

[Q]: Who succeeded Jon Pertwee as Doctor Who?
[A]: doctor who


[Q]: What is the name of the main thoroughfare in Barcelona, which runs from the Placa de Catalunya to the sea?
[A]: barcelona


[Q]: What was founded by the Rev. William and Catherine Booth in 1878?
[A]:
william booth