What is the primary gaseous component of Earth's atmosphere?

The correct choice identifies nitrogen as the primary gaseous component of Earth's atmosphere. Comprising about 78% of the atmosphere by volume, nitrogen plays a crucial role in supporting life on Earth, although it is largely inert and does not actively participate in most biological processes.

Oxygen, though essential for respiration in many living organisms and making up about 21% of the atmosphere, does not reach the same abundance as nitrogen. Carbon dioxide, while important for processes like photosynthesis, constitutes only about 0.04% and is not a major component of the atmosphere. Argon is present in trace amounts, roughly 0.93%, and does not contribute significantly to the overall composition. Understanding the proportions and the role of these gases helps clarify the structure of the atmosphere, reinforcing why nitrogen is categorized as the primary gaseous component.