Which river valley civilization was conquered over and over again because it lacked natural barriers?

As heat and pressure increase, ductile deformation becomes less likely becomes more likely is replaced by elastic deformation stops occurring

Based on this map, which statement about africa’s economic activity is most accurate? a) coastal countries are all members of opec b) economic development is more common with opec nations c) coastal countries have more access to productive resources d) economic development is more common above the sahara desert

What are canada’s major boundaries?