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]: airport : train. australia : ?
[EX A]: airplane

[EX Q]: washington : airplane. mall : ?
[EX A]: bus

[EX Q]: work : car. island : ?
[EX A]:
boat