What role do noble gases play in air composition?

Noble gases, such as helium, neon, argon, krypton, xenon, and radon, are recognized for their lack of reactivity due to their complete outer electron shells. This characteristic makes them stable and unreactive under standard conditions, meaning they do not readily participate in chemical reactions. In air composition, noble gases constitute approximately 1% of the atmosphere, primarily as argon, which is the most abundant noble gas in air. Their presence does not significantly influence the chemical behavior of the atmosphere, differentiating them from other gases that actively engage in chemical reactions.

The other options incorrectly attribute reactive behaviors or roles that noble gases do not possess; they do not assist in combustion nor do they trap heat to significantly affect global temperatures, as these functions are typically associated with greenhouse gases.