Plants are restrictive to flow of eroding agents, bind soil in their roots.
Step-by-step explanation:
Soil Erosion is the wearing away of the topmost fertile layer of soil. Topsoil gets eroded mainly due to wind, water agents.
Plants help to prevent soil from erosion in following ways :
Plants act as restriction to the speed of air & water, which are the main soil erosion agents. It also lets rain water get soaked into the ground water.
Plants roots also bind the soil tightly, & make soil stronger to be eroded by erosive agents - water, air. Eg : Shrubs , trees, grass & ground are important soil erosion preventive plants, because of their extensive root systems.
It wouldnt be a single grade being surveyed so we would choose d in additon a and b isnt national since it says 'in a certain town' and 'in a certain county'.
