TASK DEFINITION: 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.
PROBLEM: museum : bus. portland : ?

SOLUTION: car

PROBLEM: washington : airplane. spain : ?

SOLUTION: airplane

PROBLEM: airport : taxi. mainland : ?

SOLUTION:
boat