Which of these statements describes a necessary condition for civilization to develop in Mesopotamia? The presence of nearby seas allowed the regions' city-states to trade with other regions. The silt from the Euphrates and Tigris rivers created fertile soil that allowed farmers to plant year round. Abundant rainfall along the coasts of Mediterranean Sea and Persian Gulf made these regions excellent for farming. The Tigris and Euphrates rivers made it easier to protect the regions' city-states from invaders.