What are bodies of water existing below the surface of the Earth?

• A. Lakes
• B. Rivers
• C. Aquifers
• D. Reservoirs

Answer: (C)

Underground water is stored in saturated rock or soil layers, which we call groundwater. The formations that hold and transmit this water are aquifers. An aquifer acts like a natural underground reservoir, accessible through wells or springs, and it exists below the surface rather than on top of it. Lakes and rivers are surface water features, while reservoirs are usually artificial surface storages created by damming rivers. So, when the question points to water existing beneath the surface, the underground storage that fits is an aquifer. The water inside an aquifer—groundwater—can be in unconfined form, where the water table is exposed to the atmosphere, or in a confined form, trapped between impermeable layers and sometimes under pressure.