B) The shales form aquitards in the sandstone acquifer, trapping groundwater along the shale horizons that helps aid plant growth.
Explanation:
The main reason why this can take place is because shales form aquitards in the sandstone acquifer, and in this way, they trap groundwater along the shales, which helps with plant growth. Shale is a sedimentary rock that is made up of silt and clay mineral particles (what we usually call "mud"). Therefore, it belongs to the category of "mudstones."