Answer:
D. because pollutants are filtered by rock and soil deep within the earth.
Explanation:
When precipitation falls, it is usually absorbed by the earth. However, below a certain depth, the ground is saturated with water (as long as it is permeable enough). This zone is known as an aquifer. Generally, water in an aquifer is cleaner than groundwater because the rock and soil that the water has to pass through filters out pollutants. Water in aquifers can be reached by drilling wells into them and using pumps to pump it out.
