Which describes an aquifer?

An aquifer is specifically defined as a geological formation or layer that can store and transmit groundwater. This means that it consists of porous materials, such as sand, gravel, or rock, that can hold significant amounts of water. Aquifers are crucial for supplying drinking water and for agriculture because they are the sources from which wells can draw. The ability of an aquifer to yield water to wells and springs is directly related to its porosity and permeability.

In contrast, solid granite does not have the characteristics to hold or transmit water effectively, making it unsuitable as an aquifer. A layer of soil without water would not qualify as an aquifer since it lacks the groundwater essential to this definition. Lastly, a surface water body, such as a lake or river, refers to water that is above ground rather than the groundwater contained within an aquifer. Therefore, the choice specifying a layer containing groundwater aptly captures the essence of what an aquifer is.