Ответы:
Ответы: 1 - B - The passage explains the mechanism of radiocarbon dating and then discusses its limitations (age range, organic-only, calibration needs). 2 - C - The passage states the ratio remains roughly constant, because it continuously exchanges carbon with its surroundings. 3 - B - Decays here refers to the radioactive breakdown of carbon-14 over time. 4 - C - Charcoal is organic; stone, bronze, and clay are inorganic and cannot be directly dated by this method. 5 - B - The passage says fluctuations in atmospheric carbon-14 levels over millennia mean that raw radiocarbon dates require calibration. 6 - C - Too little carbon-14 remains to produce accurate results - inference: radiocarbon dating is unreliable beyond ~50,000 years. 7 - A - This correctly paraphrases both the stopping of exchange and the meaning of half-life. B, C, and D each distort the original meaning.