Final answer:
Sumeria's deterioration is attributed to agriculture failing due to increased soil salinity, which reduced wheat production and led to its dependence on other empires.
Step-by-step explanation:
Sumeria declined as c) Agriculture was coupled with declining agricultural productivity from increased salinity in their soil. As soil gets waterlogged from irrigation, salinity rises to the surface. Historians can trace the decline of wheat production: 3500 BCE- 50%, 2500 BCE- 15%, 1700 BCE- fallen by nearly 70%, causing Sumeria to become the impoverished vassal to other empires.
The decline of Sumer correlates with the issues of soil salinization that resulted from irrigation techniques. This problem, coupled with other environmental and political factors, led to a decrease in wheat yields and contributed to the region's inability to sustain its population. As a result, once preeminent in Mesopotamia, Sumer became subordinate to other burgeoning empires.