Final answer:
The Nile River helped Egypt's prosperity by providing a natural defense barrier, serving as a transportation route, and bringing fertile soil through annual floods.
Step-by-step explanation:
The Nile River played a significant role in Egypt's prosperity. It provided a natural defense barrier, served as a transportation route, and brought fertile soil through annual floods. The predictable flooding of the Nile allowed for controlled irrigation, creating nutrient-rich soil that supported agriculture and led to a surplus of food. The river also provided a constant source of drinking water for the population.