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

[Q]: Which is the only Avril Lavigne song to have reached No.1 in the US Billboard Chart?
[A]: avril lavigne


[Q]: Who played Captain Jean-Luc Picard in the television series 'Star-Trek: The Next Generation'?
[A]: jean-luc picard


[Q]: After Harold McMillan who was Britain's next Prime Minister?
[A]:
britain