A layer of rock or sediment that holds water and can range in size from a small pond to several states is called?

• A. Aquifer
• B. Well
• C. Groundwater
• D. Saturated zone

Answer: (A)

An aquifer is a layer of rock or sediment that holds groundwater in its pore spaces and fractures and can transmit water to wells. Its ability to store and move water depends on how porous and permeable it is, so it can supply groundwater over large areas. The description fits because an aquifer can vary greatly in size, from a small, localized body of water to regions spanning multiple states underground. Groundwater refers to the water itself, not the layer; a well is a structure built to access that water; and the saturated zone is the underground region where all pores are filled with water, not the storage layer itself. So the best label for that water-holding layer is an aquifer.