Which of the Following Reflects a Major Economic Difference Between

Which of the following reflects a major economic difference between sub-Saharan Africa and the rest of Afro-Eurasia?

A) Sub-Saharan Africa was isolated from trade with the Nile Valley and North Africa.
B) Sub-Saharan African agriculture was based on barley,not wheat or rice.
C) Sub-Saharan Africans valued labor more than land because of the lack of plow agriculture.
D) Sub-Saharan African land was held by chieftains who parceled it out to tenants to grow crops.