Aeroplane : Cockpit :: Train : ?

The answer is C. Engine.

The cockpit is the part of an airplane where the pilot and co-pilot sit and control the aircraft. The engine is the part of a train that provides the power to move the train.

Option A, coach, is a type of passenger car on a train. Option B, wagon, is a type of freight car on a train. Option D, compartment, is a small room on a train.

The cockpit is the most important part of an airplane because it is where the pilot and co-pilot control the aircraft. The engine is the most important part of a train because it is what provides the power to move the train.