What is an aquifer?

• A. A water body above ground
• B. A water saturated zone of soil, sand, gravel, or fractured bedrock
• C. A type of pesticide
• D. A layer of clay

Answer: (B)

An aquifer is an underground layer that stores and transmits groundwater. It’s the water-saturated zone of soil, sand, gravel, or fractured bedrock where pore spaces are filled with water and can move through the material to supply wells and springs. Aquifers can be unconfined, recharged from the surface, or confined between less-permeable layers.

The other options don’t fit because an aquifer is not a body of water above ground, nor is it a chemical used for pest control, and a single layer of clay by itself isn’t an aquifer (though clay layers can act as barriers or confining units in an aquifer system).