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. mall : ?

A: bus
****
Q: france : airplane. bermuda : ?

A: airplane
****
Q: portland : car. mainland : ?

A:
boat
****