Differences in regional economic development during the 19th century produced which of these conditions in the united states at the time of the civil war? a the north was the nation's main industrial area. b the south was the main destination for immigrants. c the north was the nation's main cotton-producing area. d the south was the nation's main transportation center for agricultural goods. i know historyguy has already answered this but he isnt the most reliable source so i just want to ask this just in case.

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 a. primary sources are historical documents, and secondary sources are modern-day documents.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.