Answer:
Option C, the rate at which the radioactive decay occurs and how much has already occurred
Explanation:
The radiometric dating is based on studying the presence/existence of parents and daughter isotopes in a sample of any substance. Based on the abundance of both the parents and daughter isotopes, the rate of decay of any radioactive substance is determined. The rate of decay of radioactive isotopes is considered to be fixed. Therefore, once the rate of decay and "radioactive decay till date" is determined, the age of the substance can be easily calculated.
Thus option C is correct
