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

[EX Q]: Of all the actors who played Doctor Who in the TV series of the same name, who appeared in the most episodes?
[EX A]: doctor who

[EX Q]: What book was written by Alexandre Dumas about Edmond Dantes' imprisonment in the Chateau d'If?
[EX A]: alexandre dumas

[EX Q]: Who resigned his army commission in 1858 to write music, such as the opera Boris Godunov and Pictures at an Exhibition?
[EX A]:
pictures at an exhibition