Answer:
D) The floodplains provided fertile soil for growing crops.
Step-by-step explanation:
The floodplains of the regions where the first civilizations emerged were very fertile because the rivers brought important nutrients with them when they flooded.
This is why the first civilizations all emerged around major rivers: Mesopotamia around the Tigris and the Euphrates, Ancient Egypt around the Nile, China around the Yellow River, and the Ancient Indian Civilization around the Hindus.