The process called menstruation.
Answer:
D
Explanation:
Vegetation on soil protects the soil from erosion because its roots and root hairs help bind the soil particles together. This occurs mechanically by binding soil into crumbs and also chemically by providing organic matter that binds the soil particle into humus that holds moisture. The soil becomes heavy to be carried off by wind erosion. Trees also break the down flow of water hence reducing the capacity of runoff to carry soil sediments.
D prevents repeating. experiments have to be repeated to be reliable.