Answer:
I really the answer to your question
Explanation:
-less attacks
-don't have to share food and water
-don't have to share other resources
-can have land
-less religious disagreements
-more time goes to farming and math and stuff like that and less to war-planning
The answer is A as river valley civilizations relied on rivers as a source of life. River valleys like Egypt, Mesopotamia and Xi, the rivers brought silt and made the soil very fertile, it also brought fresh water and fish to eat. People can also move fast using rivers.
