are low-density gases. are not abundant on Earth. have complete outermost energy levels. have two electrons in their outermost energy level.
I gave my students this multiple choice question: The noble gases, helium, neon, argon, krypton, xenon, and radon, rarely react with other elements because they

Only one answer is correct among these 4 choices:
- are low-density gases.
- are not abundant on Earth.
- have complete outermost energy levels.
- have two electrons in their outermost energy level.

Could you tell me which one is correct?

have complete outermost energy levels.