Answer:
-People settled along the river for access to water.
-The fertile delta soil produced enough crops to support the growth of a large civilization.
It was Political upheaval
Rotation.
Crop rotation is when a farmer changes the crops grown in the same field each year to ensure he gets the best harvest possible by not exhausting the soil of specific nutrients by repeatedly growing the same thing.
To save fuel and food for the troops over in europe it limited the citezens use of supplies
