Which of the following systems of trade was mostly widely used in ancient river civilizations? options:

bartering
the exchange of coined money
free exchange
international trade

I believe the answer would be international trade. I'm not fully sure though.

explanation:

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mali had been a state inside of the ghanaian empire. after ghana fell because of invading forces and internal disputes, mali rose to greatness under the leadership of a legendary king named sundiata, the "lion king." the songhai empire, already weakened by internal political struggles, went into decline.