The correct answer is a) nitrogen. Noble gases are a group of chemical elements that are characterized by their lack of reactivity due to having full valence shell of electrons. This group includes helium, neon, argon, krypton, xenon, and radon.
Nitrogen, on the other hand, is not a noble gas; it belongs to the group of nonmetals and is quite reactive. In the Earth’s atmosphere, nitrogen makes up about 78% of the air, and it readily forms compounds with other elements, unlike the noble gases, which are found in the atmosphere in their elemental form.