For this question, letter D is the right answer. This method is still done up to this modern time as this is effective and efficient in growing crops even in mountainous areas. This was widely used by ancient civilization living in hilly terrains to have a source of food for their community.
A sloped terrain is cut in such a way that resembles steps as it has a purpose. When rain falls, excess water from each step will flow down to provide water to the bottom steps of the terrace and removing unwanted water. This technique also decreases erosion and flashfloods keeping the people living at the bottom of the terrace safe from disasters.
The areas that is most affected by freguent water pollution is in the coast of brazil