The Expansion of Bantu-Speaking Peoples Through Much of Sub-Saharan Africa

The expansion of Bantu-speaking peoples through much of sub-Saharan Africa has been tied to what process?

A) the introduction of bananas, taro, and Asian yams
B) the development of efficient slash and burn agricultural techniques
C) the introduction of Near Eastern cereal crops
D) the development of pastoralism
E) conquest by militaries