Which of the following increases the likelihood of groundwater contamination?

The correct choice indicates that shallow groundwater significantly increases the likelihood of groundwater contamination. When groundwater is located close to the surface, any pollutants or contaminants introduced in the surrounding area have a much shorter distance to travel before reaching the water supply. This makes it easier for chemicals, pesticides, or other harmful substances to seep into the groundwater, potentially affecting drinking water and nearby ecosystems.

Conversely, clay soil and hard-packed surfaces can act as barriers to contaminants, reducing their movement into the groundwater. Vegetated areas typically promote absorption and filtration of substances, further helping to protect groundwater quality. Therefore, the closeness of groundwater to the land surface enhances the risk of contamination, underscoring the importance of monitoring activities near such regions.