Answer the following question given this paragraph: 

Radioactive decay is the breakdown of unstable isotopes into stable elements. For example, carbon-14 is an unstable isotope of carbon that decays to the stable element nitrogen-14. The rate of decay of an isotope is measured in half-lives. A half-life is the time it takes for half a given amount of an isotope to decay.


Q: What is the term for the breakdown of unstable isotopes into stable elements?

 Choices:

- isotopic decay

- radioactive decrease

- secondary decay

- radioactive decay

A:
radioactive decay
