Answer:D.the water table
Explanation: when wells are dug , they are dug to the point where all the pore spaces are completely saturated so that they can be filled up with water, when the water table is reached.
This is where groundwater fills the sediments and porous rocks or cracked rocks.
Above the water table we find the unstaturated zone which is called zone of aeration since it is made up of soil that contains oxygen.
The height of water table depends on the land surface above it. The source of groundwater is rain , during precipitation water get seeped through soil surface . Changes in precipitation are responsible for the level of groundwater.