Permeable rock strata or sediment that transmit groundwater freely are called

Aquifers

Explanation:

An aquifer is an underground layer of water that bears preamble rocks and thus is composed of the silt, sand dad gravel ad thus is rechargeable surface below the ground and occurs at a level of 30,000 feet. And also is affected by the supply of the water ad irrigation. It is classified as the saturated and the unsaturated water and the confined and the unconfined content that is represented by this impermeable rock.

I'm pretty sure it's c. extremely gradual but not 100% sure though.