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


[Q]: theater : car. museum : ?
[A]: bus


[Q]: portland : car. australia : ?
[A]:
airplane