What term indicates the process in which unstable atomic nuclei release radiation?

The term that indicates the process in which unstable atomic nuclei release radiation is: radioactive decay

When a radioactive matter is released without the protective container, it will release all of its energy in form of radiation until all of the energy eventually faded away.
This radiation will be really dangerous for most of the organisms around it, and will make the environment around it became unhabitable.

To be honest i thinks its between the first answer and the third answer