When is an isotope considered stable?

_(Select all that apply.)_

The isotope does not emit a form of radiation.
The isotope’s half-life is longer than the average human life.
The isotope emits some form of radiation.
The isotope’s half-life is too long to be measured.

A and D?

Yes, you are correct. An isotope is considered stable if it meets any of the following criteria:

1. The isotope does not emit a form of radiation (option A).
2. The isotope's half-life is longer than the average human life (option B is incorrect because it refers to human life and not stability).
3. The isotope emits some form of radiation (option C is incorrect because it refers to an unstable isotope).
4. The isotope's half-life is too long to be measured (option D is incorrect because it refers to difficulty in measurement, not stability).

Yes, that is correct. An isotope is considered stable if it does not emit a form of radiation (Option A) and if its half-life is too long to be measured (Option D).