Slavery Took on Different Forms Depending Upon the Political Economies

Slavery took on different forms depending upon the political economies and demographic features of the agricultural state society. For example, in some African societies, slavery corresponded to an "open system" in which slaves could be incorporated into domestic kin groups and even become upwardly mobile. In contrast, "closed systems" of slavery provided no opportunities for upward mobility or incorporation into kin groups. The open system of slavery occurred:

A) where land was scarce and population density high
B) where land was relatively abundant and less populated
C) in areas that had rigid caste systems such as Greece, Rome, and China
D) when there was a lot of surplus generated from agriculture, and new markets needed to be opened to accommodate the distribution of this excess wealth