what were the four river valley civilizations?
city-states

valley

Mesopotamian city-states

Ancient Egypt

Indus Valley

Ancient China

Explanation:

The initial four major civilization developed along river valleys. The reason for that was that these civilizations were based on agriculture, and the river valleys of the large rivers provided perfect conditions for large scale farming of crops. Three of these civilizations were in Asia and one in Africa. The ones in Asia were Ancient China along the Huang He River, Indus Valley along the Indus and Saraswati rivers, and the Mesopotamian city-states along the Tigris and Euphrates rivers. In Africa, in its northeastern part, it was the Ancient Egyptian civilization along the Nile River.

well the fact it is basically a peninsula allowed trade to come from many places, thus allowing cultural diffusion to take place. india has seasonal monsoons that merchants travel back and forth from india using the monsoons wind patterns