Why are the earliest americans known as prehistoric indians? a: because they built burial mounds. b: because they did not have a written language. c: because they did not have tools. d: because they had vast library systems.

The earliest Americans are known as prehistoric Indians because B. They didn't have a written language.

If we break down the word "prehistory", we can understand it better. The prefix pre- means before, so we can conclude that the word "prehistory" means before history, or before there were written records of these civilizations. It is more difficult for historians to understand these times because they must infer what they know from archaeological digs and artifacts that have been found rather than from written records from the time.

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i would think it's industries and hydroelectric power