What percentage of the atmosphere is constituted by nitrogen?

The correct answer reflects that approximately 78.6% of the Earth's atmosphere is composed of nitrogen. This high percentage indicates nitrogen's role as the most abundant gas in the atmosphere, which is significant for various biological and physical processes. Nitrogen is largely inert and does not readily react with other substances, making it an essential component that does not heavily influence climatic changes or the greenhouse effect like other gases do.

In contrast, oxygen makes up around 21.4% of the atmosphere, playing a crucial role in respiration and combustion processes. The other options presented are inaccurately low or high compared to the known atmospheric composition, emphasizing how nitrogen dominates the gaseous makeup of the atmosphere, ensuring its stability and preserving conditions suitable for life.