Molecules in all organisms are composed in part of radioactive carbon-14. Which statement best explains the presence of carbon-14 in organisms?

Carbon-14 is an isotope of carbon, so it has the same number of electrons as stable carbon isotopes and behaves similarly in chemical reactions. Organisms take in carbon through food or photosynthesis and use it to build molecules, including molecules containing carbon-14. The isotope does not need to react faster or undergo nuclear reactions in the body.

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