Agricultural societies cannot exist without staple crops.Several food plants, such as kola and okra, are known to have been domesticatedin western Africa, but they are allsupplemental, not staple, foods. All the recorded staple crops grown in westernAfrica
were introduced from elsewhere,beginning, at some unknown date, with rice and yams. Therefore, discoveringwhen rice and yams were introduced into western Africawould establish the earliest date at which agricultural societies could havearisen there.
Which of the following is an assumption on which theargument depends?
A. People in western Africadid not develop staple crops that they stopped cultivating once rice and yamswere introduced.
B. There are no plants native to western Africathat, if domesticated, could serve as staple food crops.
C. Rice and yams were grown as staple crops by the earliestagricultural societies outside of western Africa.
D. Kola and okra are better suited to growing conditions inwestern Africa than domesticated rice and yamsare.
E. Kola and okra were domesticated in western Africa before rice and yams were introduced there.
