Here's a problem to solve: The noble gases, helium, neon, argon, krypton, xenon, and radon, rarely react with other elements because they

Among the 4 following options, which is the correct answer?

- A: are low-density gases.
 
- B: are not abundant on Earth.
 
- C: have complete outermost energy levels.
 
- D: have two electrons in their outermost energy level.
 