The correct answer is A. Water : Boat.
A train travels on a track, just as a boat travels on water. A bullet travels through a barrel, but it is not necessary for the bullet to have a barrel in order to travel. An idea does not need a brain in order to exist, and fame does not need television in order to exist.
In addition, trains and boats are both vehicles that are used for transportation. Bullets and barrels are both tools that are used for shooting. Ideas and brains are both things that are used for thinking. Fame and television are both things that are used for recognition.
Therefore, the answer that best completes the analogy "Train : Track" is "Water : Boat."
