Concept:Earthworms enhance soil health by modifying the physical arrangement of soil particles.Explanation:Earthworms burrow through the soil, creating channels that improve aeration, drainage, and root movement.They also ingest soil and organic matter, then excrete casts that bind soil particles together.This binding forms stable aggregates and improves the soil's overall physical condition.These changes relate to soil structure, not to soil texture, pathogens, or erosion control.Answer:D. improves soil structure