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

Formerly known as Sky Dome, Rogers Centre is home to what American League baseball team, the only MLB team located outside the United States?
american league

Physics. What is the SI unit for amount of substance?
amount of substance

Which song title links a 1957 single release by Carl Perkins and a 1963 single by the Dave Clark Five?

the dave clark five