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

[Q]: What is the SI unit of capacitance?
[A]: capacitance


[Q]: What city is closest to Copacabana beach?
[A]: copacabana, rio de janeiro


[Q]: The Sumida and Arakawa are two main rivers of which capital city?
[A]:
arakawa, tokyo