Given a factoid/trivia type question, generate the topic of the question. The topic is the entity the question talks about.
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Question: Of all the actors who played Doctor Who in the TV series of the same name, who appeared in the most episodes?

Answer: doctor who

Question: Which novel by A J Cronin is credited with laying down the foundation in Great Britain for the introduction of the National Health Service?

Answer: a. j. cronin

Question: Which 1959 Alfred Hitchcock film had the tagline 'Its a deadly game of tag and Cary Grant is it!'?

Answer:
alfred hitchcock