Compare the emergence of advanced civilizations in meso and south america with the four early river valley civilizations. which of the following systems of trade was most widely used in both ancient river civilizations and ancient native american civilizations? bartering the exchange of coined money free exchange international trade

What is the main difference between primary and secondary sources? a. primary sources are historical documents, and secondary sources are modern-day documents. b. primary sources are derived from museums and archives, and secondary sources are created by history students and academics. c. primary sources are found in ancient places with a rich history, and secondary sources are found in historical journals and blogs. d. primary sources are created during a particular historical era, and secondary sources are created by studying primary sources.