Two analogies that relate places/locations to the associated travel mode is given in the form "A : B. C : ?". "A : B" relates place A to travel mode B. Your task is to replace the question mark (?) with the appropriate travel mode for the given place C, following the "A : B" relation.

[Q]: spain : airplane. moon : ?
[A]: rocket


[Q]: park : bicycle. hospital : ?
[A]: ambulance


[Q]: canada : bus. airport : ?
[A]:
train