The age of fossils can sometimes be determined by radiometric dating is called

17,190 years

Explanation:

Each isotope has a characteristic half-life, which is the time required for half of that isotope to decay. After one half-life has elapsed, 50% of the isotope has decayed and 50% remains. After two half-lives, 75% has decayed and 25% remains. After three half-lives, 87.5% has decayed and 12.5% remains. For carbon-14, which has a half-life of 5,730 years, three half-lives corresponds to 17,190 years.

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which are human systems?

the amazon rain forest

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the north american free trade agreement