What is a colorless, odorless, and inert gas that makes up 78% of air?

The answer is correct because nitrogen is a colorless and odorless gas that constitutes approximately 78% of the Earth's atmosphere. Being inert means that it does not readily react with other chemicals, making it stable and non-toxic at the concentrations found in the air. Nitrogen plays a crucial role in various biological processes, including being an essential component of amino acids and nucleic acids, yet it remains largely unreactive in its gaseous form, which is why it is often referred to as inert.

Oxygen, while essential for respiration in living organisms, comprises about 21% of the air and has distinct properties, including being reactive and supporting combustion. Carbon dioxide, another important gas in the atmosphere, is present in much smaller quantities (around 0.04%) and is associated with respiration and photosynthesis processes. Hydrogen, although the most abundant element in the universe, is not a major component of the Earth's atmosphere by volume.