Answer:
B: through migratory patterns
Explanation:
Although we can't discard completely the other three options, it is most likely that the early tribes learned about other people trough migratory patterns. Many tribes were nomadic people who primarily were hunters-gatherers. Therefore they would have known about each other observing their migratory patterns. Because archeologists have found remnants in different areas, it is believed that the different bands communicated, perhaps even trading among each other.