Correct Option: C

In the boiler of a steam engine, there is a firebox where coal is shoveled into. The coal is kept burning at a very high temperature, and is used to heat the boiler to boil water producing a high pressure steam. The high-pressure steam expands and exits the boiler via steam pipes into the steam reservoir, the steam is then controlled by a slide valve to move into a cylinder to push the piston. The pressure of the steam energy pushing the piston turns the drive wheel in a circle, creating motion for the locomotive.