Which soil condition is most favorable for the removal of viruses?

The soil condition that is most favorable for the removal of viruses is characterized by fine loamy sand over coarse sand and gravel. This combination offers a balance of porosity and surface area which enhances the filtration and adsorption processes critical for removing viruses from water.

Fine loamy sand can effectively capture smaller particles, including viruses, because it provides a greater surface area for adhesion. It retains moisture better than coarser materials, allowing for a more prolonged contact time between the virus and soil particles. The underlying coarse sand and gravel facilitate good drainage, preventing water from saturating the soil too quickly and allowing the finer material above to maintain its filtering capacity longer.

This combination creates a favorable environment for microbial activity, which can also contribute to the breakdown and removal of viruses. This correct answer reflects the optimal conditions where both the physical and biological interactions within the soil medium are conducive to decreasing viral contamination in groundwater systems.