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Correct Answer: erosion
the correct answer to the question is "erosion." let's delve deeper into why this is the case.
erosion is a geological process where soil, rock, and other surface materials are worn away and then transported from one place to another. this movement can be caused by agents like water, wind, ice, or gravity. in the scenario described in the question—muddy soil being carried away by water draining down the sidewalk after a rainstorm—the key agent of erosion is water.
when it rains heavily, the force of the water flowing over the land can pick up loose soil and sediment. this is particularly common in areas where the ground is not covered by vegetation, which would normally help hold the soil in place. the moving water drags these particles along with it as it moves, a process known as water erosion. in urban areas, where natural soil is often covered by impermeable surfaces like concrete, rainwater tends to flow along streets and sidewalks, picking up not only soil but also pollutants and debris, carrying them toward drainage systems or natural water bodies.
the alternative answer choice, "gravity," is related to erosion but is not the best answer in this context. gravity indeed plays a role in all forms of erosion by pulling water and sediment downhill. however, gravity alone does not encompass the broader process of material being detached, transported, and redeposited, which defines erosion. gravity is a force that influences erosion but is not a type of erosion itself.
in summary, erosion is the correct answer because it specifically describes the process of transporting weathered and loosened material, like soil, from one location to another through agents such as water. this is exactly what happens when rainwater carries muddy soil down the sidewalk after a storm. the transported soil eventually settles in new locations, a phase known as deposition, which typically follows erosion but is a distinct process focused on the accumulation of materials rather than their removal and movement.
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