The earliest civilizations developed in the river valleys of: "A. the Nile River" and "D. the Tigris <span>and Euphrates Rivers" since these areas were the most fertile--meaning that crops were able to grow far more easily</span>
The correct options are: "The Nile River - The Tigris and Euphrates Rivers"
The Nile was a fundamental element for the flourishing of the civilization of Ancient Egypt. Most of the population and cities were in the valley of the Nile and the Delta. The Nile was vital to Egyptian culture since the Stone Age. Climate change, and desertification, dried up Egypt's hunting and grazing lands to form the Sahara Desert, around 8,000 BC; then the inhabitants emigrated and settled next to the Nile River, where they developed an agricultural economy and a centralized society.
Mesopotamia is the name by which the zone of the Near East located between the Tigris and Euphrates rivers is known, although it extends to the fertile zones contiguous to the strip between both rivers, and that approximately agrees with the non-desert areas of the current Iraq and the border area of the north-east of Siria.El term refers mainly to this area in the Ancient Age that was divided into Assyria (to the north) and Babylon (to the south). Babylon (also known as Chaldean), in turn, was divided into Acadia (upper part) and Sumeria (lower part). Its rulers were called patesi.
