Answer:
c) Trade
Step-by-step explanation:
Bantu peoples, A group of African language speakers (Bantu languages) that originally lived in the notch of western Africa.
In around 1500 B.C.E., the Bantu speakers stumbled upon the domestication of yams and bananas. They began domesticating goats around the same time, as well.
The Bantu were soon migrating out from their homeland to the south and east of the Sahara. Much like how the Mesopotamians migrated into Europe as they taught the natives about wheat, it's possible that the Bantu migrated for the same reason, with only a small number of people leaving their homes to 'trade' away the secrets of agriculture.