Possible reasons for the interaction between pastoral and agrarian societies include
1.changes in climate
2.overpopulation
3.the development of trade routes
4.strong nomadic leadership wanting to expand their lands

(4.) strong nomadic leadership wanting to expand their lands

Explanation:

- "made the south's economy grow rapidly and a small effect that a lot of people don't know is that it made the more demand of slaves and cotton products. and also new states formed due to plantations growing in size."

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answer; /// i do believe that the correct answer is (a); a farming tribe that settled primarily along the mississippi and arkansas rivers;