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Agriculture and iron working probably spread to Africa from neighboring regions. A. Once Africans developed their own crops, they no longer borrowed from other regions. B. The harshness of the African climate meant that agriculture could not develop until after the introduction of iron tools. C. The use of livestock improved transportation and trade and allowed for new forms of political control. D. As the Sahara expanded, the camel gained in importance, eventually coming to have religious significance. E. The spread of iron working had far-reaching effects on social, economic, and political organization in Africa. F. Today's Bantu-speaking peoples are descended from a technologically advanced people who spread throughout Africa.