Which of the following best describes an aquifer?

An aquifer is defined as a water-bearing formation that can store and transmit water. This geological formation typically consists of permeable materials such as sand, gravel, or limestone, which allow water to move through it. Aquifers serve as crucial water resources, as they can supply water for various uses, including agriculture, drinking, and industrial processes.

The character of an aquifer involves its capacity to store groundwater and its ability to let that water flow freely when tapped by wells or other extraction methods. The aquifer's properties, such as porosity and permeability, determine how much water it can hold and how easily that water can be accessed.

Other options relate to components of the water cycle but do not encapsulate the full definition of an aquifer. For instance, a bedrock layer may serve as a foundation for an aquifer but is not inherently a water-bearing formation. A recharge zone refers to areas where water can enter an aquifer but is not the aquifer itself. A surface water source, such as a river or lake, pertains to water found above ground rather than underground storage found in aquifers. Thus, describing an aquifer primarily as a water-bearing formation is accurate and precise.