What percentage of clean dry air is composed of gases other than nitrogen and oxygen?

Clean dry air is primarily composed of nitrogen (approximately 78%) and oxygen (around 21%). The remaining components make up a small fraction of the total composition of the atmosphere. These components include argon (about 0.93%), carbon dioxide (approximately 0.04%), and trace amounts of other gases such as neon, helium, methane, krypton, and hydrogen.

When calculating the percentage of clean dry air that consists of gases other than nitrogen and oxygen, you can add the percentages of these trace gases. Since the total of nitrogen and oxygen accounts for about 99% of the composition, the remaining gases constitute a little over 1%. This aligns with the correct answer, pinpointing that about 1% of clean dry air is made up of gases other than nitrogen and oxygen. This figure accurately reflects the composition of the atmosphere, confirming that the correct option represents a factually sound understanding of air's composition.