Given an trivia question precisely answer the question with a word/phrase/name. External resources such as Wikipedia could be used to obtain the facts.

[EX Q]: Three of the Galilean moons of Jupiter are Io, Europa and Callisto. Which is the fourth?
[EX A]: ganymede

[EX Q]: With the symbol H what is the unit of inductance?
[EX A]: henry

[EX Q]: Which London art gallery is situated in a Victorian mansion in Manchester Square?
[EX A]:
wallace collection