<span>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.</span>
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<span>There had been German failures in the past, failures that must be set against the successes of France and Britain.By the end of the Middle Ages, which had seen Britain and France emerge as unified nations, Germany remained a crazy patchwork of some three hundred individual states.But there was the disaster of religious differences which followed the Reformation.</span>
Memel went from being under control of the German empire and into the control of Lithuania
The reason why earlier historians consider the medieval periods the "dark ages: is : the era seemed less important than the renaissance and the roman empire
there was no significant societal progress during this age
hope this helps
It explained the specific ways in which England allegedly failed the colonies.