Given the question: Information: - On a steam locomotive, a trailing wheel or trailing axle is generally an unpowered wheel or axle (wheelset) located behind the driving wheels. The axle of the trailing wheels is usually located in a trailing truck. On some large locomotives, a booster engine was mounted on the trailing truck to provide extra tractive effort when starting a heavy train and at low speeds on gradients. - On a steam locomotive, a driving wheel is a powered wheel which is driven by the locomotive's pistons (or turbine, in the case of a steam turbine locomotive). On a conventional, non-articulated locomotive, the driving wheels are all coupled together with side rods (also known as coupling rods); normally one pair is directly driven by the main rod (or connecting rod) which is connected to the end of the piston rod; power is transmitted to the others through the side rods. - The Whyte notation for classifying steam locomotives by wheel arrangement was devised by Frederick Methvan Whyte, and came into use in the early twentieth century following a December 1900 editorial in "American Engineer and Railroad Journal". The notation counts the number of leading wheels, then the number of driving wheels, and finally the number of trailing wheels, groups of numbers being separated by dashes. Other classification schemes, like UIC classification and the French, Turkish and Swiss systems for steam locomotives, count axles rather than wheels. - In the Whyte notation for the classification of steam locomotive wheel arrangement , a 2 - 4 - 4 - 0 is a locomotive with two leading truck , two sets of four driving wheels , and no trailing truck . Examples of this type were constructed as Mallet locomotives . - A steam engine is a heat engine that performs mechanical work using steam as its working fluid. - A fuel is any material that can be made to react with other substances so that it releases chemical or nuclear energy as heat or to be used for work. The concept was originally applied solely to those materials capable of releasing chemical energy but has since also been applied to other sources of heat energy such as nuclear energy (via nuclear fission and nuclear fusion). - Rail transport is a means of conveyance of passengers and goods on wheeled vehicles running on rails, also known as tracks. It is also commonly referred to as train transport. In contrast to road transport, where vehicles run on a prepared flat surface, rail vehicles (rolling stock) are directionally guided by the tracks on which they run. Tracks usually consist of steel rails, installed on ties (sleepers) and ballast, on which the rolling stock, usually fitted with metal wheels, moves. Other variations are also possible, such as slab track, where the rails are fastened to a concrete foundation resting on a prepared subsurface. - Frederick Methvan Whyte (March 2, 1865 1941) was a mechanical engineer of Dutch background who worked for the New York Central in the United States. He is most widely known as the person who developed Whyte notation to describe the different wheel arrangements of steam locomotives in 1900. - John Blenkinsop (1783 22 January 1831) was an English mining engineer and an inventor of steam locomotives, who designed the first practical railway locomotive. - A locomotive or engine is a rail transport vehicle that provides the motive power for a train. The word originates from the Latin "loco" "from a place", ablative of "locus", "place" + Medieval Latin "motivus", "causing motion", and is a shortened form of the term "locomotive engine", first used in the early 19th century to distinguish between mobile and stationary steam engines. - A steam locomotive is a railway locomotive that produces its pulling power through a steam engine. These locomotives are fueled by burning combustible materialusually coal/coke, wood, or oilto produce steam in a boiler. The steam moves reciprocating pistons which are mechanically connected to the locomotive's main wheels (drivers). Both fuel and water supplies are carried with the locomotive, either on the locomotive itself or in wagons (tenders) pulled behind. The first steam locomotive, made by Richard Trevithick, first operated on 21 February 1804, three years after the road locomotive he made in 1801. The first practical steam locomotive was built in 1812-13 by John Blenkinsop. - A piston is a component of reciprocating engines, reciprocating pumps, gas compressors and pneumatic cylinders, among other similar mechanisms. It is the moving component that is contained by a cylinder and is made gas-tight by piston rings. In an engine, its purpose is to transfer force from expanding gas in the cylinder to the crankshaft via a piston rod and/or connecting rod. In a pump, the function is reversed and force is transferred from the crankshaft to the piston for the purpose of compressing or ejecting the fluid in the cylinder. In some engines, the piston also acts as a valve by covering and uncovering ports in the cylinder wall. The petrol enters inside the cylinder and the piston moves upwards and the spark plug produces spark and the petrol is set on fire and it produces an energy that pushes the piston downwards. - In rail transport, a wheel arrangement or wheel configuration is a system of classifying the way in which wheels are distributed under a locomotive. Several notations exist to describe the wheel assemblies of a locomotive by type, position, and connections, with the adopted notations varying by country. Within a given country, different notations may also be employed for different kinds of locomotives, such as steam, electric, and diesel powered. - Steam is water in the gas phase, which is formed when water boils. Steam is invisible; however, "steam" often refers to wet steam, the visible mist or aerosol of water droplets formed as this water vapour condenses. At lower pressures, such as in the upper atmosphere or at the top of high mountains, water boils at a lower temperature than the nominal at standard pressure. If heated further it becomes superheated steam. - Richard Trevithick (13 April 1771 22 April 1833) was a British inventor and mining engineer from Cornwall, England. The son of a mining captain, and born in the mining heartland of Cornwall, Trevithick was immersed in mining and engineering from an early age. He performed poorly in school, but went on to be an early pioneer of steam-powered road and rail transport. His most significant contribution was the development of the first high-pressure steam engine. He also built the first full-scale working railway steam locomotive. On 21 February 1804 the world's first locomotive-hauled railway journey took place as Trevithick's unnamed steam locomotive hauled a train along the tramway of the Penydarren Ironworks, in Merthyr Tydfil, Wales. - A boiler is a closed vessel in which water or other fluid is heated. The fluid does not necessarily boil. (In North America, the term "furnace" is normally used if the purpose is not to actually boil the fluid.) The heated or vaporized fluid exits the boiler for use in various processes or heating applications, including water heating, central heating, boiler-based power generation, cooking, and sanitation. What object entity has the relation of 'subclass of' with the subject '2-4-4-0'? Choices: - articulated locomotive - background - boiler - case - coal - concept - configuration - count - country - coupling - driving - dutch - editorial - engine - engineer - engineering - england - english - fluid - force - french - fusion - gas - heat - heat engine - locomotive - march - material - mining - notation - person - phase - position - power - pump - rail - rail transport - road - road transport - rolling stock - running - steam turbine locomotive - stock - temperature - top - track - truck - turbine - type - vessel - wall - water - water heating - wheel - wood - word - work - world
The answer is:
articulated locomotive