People of the classical era found the flat, open geography of the african plains particularly well suited to:
a. harvesting trees for lumber
b. herding livestock
c. developing naval technology
d. growing crops

People of the classical era found the flat, open geography of the African plains particularly well suited to herd livestock as it enabled them to keep steady amounts of live animals at one location without loosing sight of their whereabouts - b. They had difficulties growing crops on the African plains. 

The u.s. got world power