Answer: Carbon-14
Explanation:
Carbon dating the procedure which is used for the substances which is used to date the substances less than 40,000.
This method is based on an unstable isotope of carbon that living animals and plants incorporate inside it.
When the organisms are alive the ratio of stable isotope inside the organism is same to the ratio that is found in the atmosphere.
As the organism dies the carbon 14 gets converted into nitrogen 14. By measuring both the ratios, the relative age can be determined.
