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]: What nickname is given to the Australian Association Football International team?
[A]: australia


[Q]: Appaloosa, Tennessee Walking, and Arabian are all types of what?
[A]:
arabian horse