Quickly! ) which geographic factors contributed to the decline of sumer? choose all answers that are correct. a. irrigation of the crops led 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.

A, B and D all contributed to Sumer's decline. In the case of A, irrigation caused the salt content of the soil to rise which made it very difficult to utilize for agriculture. As in B, Sumer had no natural barrier and was located on a flat space, making the land susceptible to weather and war. With D, the land became too wet (swampy) and could not be farmed.