Which geographic factor led to the decline of Sumer? Choose all that are correct. A. There was no river / water access for farming B. it was located in a flat plain, and isolated from trade routes. C. The Tigris and Euphrates rivers flooded every year, leaving behind dark, fertile soil D. The cultivated soil had poor drainage and caused salt deposits to be left behind in the soil

D. The cultivated soils had poor drainage and caused salt deposits to be left behind in the soil.

Explanation:

Mesopotamian civilisation is known as the land between two rivers, the Tigris lied in the north and Euphrates lied in the south. the region used to experience seasonal rainfall due to which the land was flooded in the winter and spring while the water was scarce during the other seasons. Mesopotamia was scarce of the resources. Historians consider war and environmental changes as the main reason for its decline. Irrigation techniques utilised by the Mesopotamian also played an important role in its decline because if we leave irrigation water on the fields to evaporate it leaves behind mineral salts. These salt concentrate on the upper layer of the soil, it is poisonous for the soil. The concentration of salts was the main reason for its collapse.