In most early civilizations, people were able to grow a surplus of food and to manufacture local specialty items such as pottery. what was one result of these activities?   a. people in widely separated geographical locations developed a system of trade. b. people  became more isolated because they had no need to associate with other groups. c. people exchanged new ideas and developed a system of government centered around democratic principles. d. people became more warlike because they raided their neighbors for products they could not make themselves.