Item Starting around 7,000 years ago, Native Americans started mining copper by digging underground mines. What explains this behavior? Choose the correct answer.
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By mining underground they were able to turn copper into a renewable resource.
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The costs of surface mining were much lower than the costs of underground mining.
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They believed the benefits would outweigh the cost of the extra effort needed to mine
underground
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The copper located underground was found at a lower concentration than the copper located
along the surface.
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Item 1
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