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.

[EX Q]: mars : spaceship. airport : ?
[EX A]: train

[EX Q]: store : car. moon : ?
[EX A]: rocket

[EX Q]: mainland : boat. washington : ?
[EX A]:
train