Explanation:
1. Federalism
2. The U.S. Constitution
3. Checks and Balances ( The legislative,Executive, Judicial Branch)
4. Popular Sovereignty
The Bill of Rights because it gave power to the states and national government bringing balance.
The African empires remained largely as traditionalists and agriculturists. They stayed in their territories working hard to achieve progress. The Swahili city-states were traders and craftsmen. Their culture had been influenced by Middle-Easters and Indian territories. They were able to make dealings with overseas territories which helped them increase their economy.
I would go with the last option.
