Which geographic factors contributed to the decline of Sumer? Choose all answers that are correct. A. Irrigation of the crops le
d to salinization of the soil. B. Sumer was located on a flat plain that provided no natural barriers to invasion. C. Mountains made agriculture difficult. D. The land became too swampy to grow adequate crops.
It's A Irrigation was overused, the soil didn't get any rest (crop rotation is a younger invention), the result was salinization of the soil, which led to decline of Sumer.
