In this task, you are given a context, a subject, a relation, and many options. Based on the context, from the options select the object entity that has the given relation with the subject. Answer with text (not indexes).

Context: A sluice (from the Dutch "sluis") is a water channel controlled at its head by a gate. A mill race, leet, flume, penstock or lade is a sluice channelling water toward a water mill. The terms sluice, sluice gate, knife gate, and slide gate are used interchangeably in the water and wastewater control industry., A reservoir (etymology: from French "réservoir" a "storehouse" ) is a storage space for fluids. These fluids may be water, hydrocarbons or gas. A reservoir usually means an enlarged natural or artificial lake, storage pond or impoundment created using a dam or lock to store water.
Reservoirs can be created by controlling a stream that drains an existing body of water. They can also be constructed in river valleys using a dam. Alternately, a reservoir can be built by excavating flat ground and/or constructing retaining walls and levees., A bucket or pail is typically a watertight, vertical cylinder or truncated cone, with an open top and a flat bottom, attached to a semicircular carrying handle called the "bail"., A mill race , millrace or millrun is the current of water that turns a water wheel , or the channel ( sluice ) conducting water to or from a water wheel . Compared to the broad waters of a mill pond , the narrow current is swift and powerful . The race leading to the water wheel on a wide stream or mill pond is called the head race ( or headrace ) , and the race leading away from the wheel is called the tail race ( or tailrace ) . A mill race has many geographically specific names , such as leat , lade , flume , goit , penstock . These words all have more precise definitions and meanings will differ elsewhere . The original undershot waterwheel , described by Vitruvius was a run of the river wheel placed so a fast flowing stream would press against and turn the bottom of a bucketed wheel . In the first meaning of the term , the millrace was the stream ; in the sense of the word , there was no channel , so no race . As technology advanced , the stream was dammed forming a weir . This increased the head of water . Behind the weir was the millpond , or lodge . The water ( millrace ) was channelled to the waterwheel by a sluice or millrace - this was the head race . From the waterwheel , the water was channelled back to the stream by a sluice known as the tail race . When the tail race from one mill led to another mill where it acted as the head race this was known as the mid race . The level of water in the millrace could be controlled by a series of sluice gates ., A water wheel is a machine for converting the energy of free-flowing or falling water into useful forms of power, often in a watermill. A water wheel consists of a large wooden or metal wheel, with a number of blades or buckets arranged on the outside rim forming the driving surface. Most commonly, the wheel is mounted vertically on a horizontal axle, but the tub or Norse wheel is mounted horizontally on a vertical shaft. Vertical wheels can transmit power either through the axle or via a ring gear and typically drive belts or gears; horizontal wheels usually directly drive their load., A mill pond (or millpond) is a body of water used as a reservoir for a water-powered mill., A gear or cogwheel is a rotating machine part having cut "teeth", or cogs, which mesh with another toothed part to transmit torque. Geared devices can change the speed, torque, and direction of a power source. Gears almost always produce a change in torque, creating a mechanical advantage, through their gear ratio, and thus may be considered a simple machine. The teeth on the two meshing gears all have the same shape. Two or more meshing gears, working in a sequence, are called a gear train or a "transmission". A gear can mesh with a linear toothed part, called a rack, thereby producing translation instead of rotation., A blade is the portion of a tool, weapon, or machine with an edge that is designed to puncture, chop, slice or scrape surfaces or materials. A blade may be made from a flaking stone, such as flint, metal (usually steel), ceramic, or other material. Blades are one of humanity's oldest tools, and continue to be used for combat, food preparation, and other purposes., A watermill or water mill is a mill that uses moving water as its power source. It is thus a structure that uses a water wheel or water turbine to drive a mechanical process such as milling (grinding), rolling, or hammering. Such processes are needed in the production of many material goods, including flour, lumber, paper, textiles, and many metal products. Thus watermills may be gristmills, sawmills, paper mills, textile mills, hammermills, trip hammering mills, rolling mills, wire drawing mills, and so on., A flume is a human-made channel for water in the form of an open declined gravity chute whose walls are raised above the surrounding terrain, in contrast to a trench or ditch. Flumes are not to be confused with aqueducts, which are built to transport water, rather than transporting materials using flowing water as a flume does. Flumes route water from a diversion dam or weir to a desired materiel collection location., A machine is a tool containing one or more parts that uses energy to perform an intended action. Machines are usually powered by chemical, thermal, or electrical means, and are often motorized. Historically, a power tool also required moving parts to classify as a machine. However, the advent of electronics has led to the development of power tools without moving parts that are considered machines., A penstock (fr. "conduite forcée") is a sluice or gate or intake structure that controls water flow, or an enclosed pipe that delivers water to hydro turbines and sewerage systems. It is a term that has been inherited from the earlier technology of mill ponds and watermills., Subject: mill race, Relation: subclass_of, Options: (A) body of water (B) channel (C) collection (D) constructing (E) direction (F) ditch (G) diversion dam (H) drawing (I) driving (J) dutch (K) electronics (L) food preparation (M) forming (N) french (O) gas (P) gate (Q) human (R) industry (S) knife (T) lake (U) machine (V) mill (W) natural (X) number (Y) paper (Z) pipe ([) power source (\) preparation (]) process (^) ratio (_) reservoir (`) river (a) rotation (b) sequence (c) sluice (d) steel (e) storage (f) structure (g) technology (h) term (i) textile (j) tool (k) top (l) torque (m) train (n) transport (o) turbine (p) via (q) water (r) weapon (s) weir (t) wheel (u) wire
body of water