Air is made up of different gases such as oxygen, nitrogen and carbon dioxide. How would you best describe these three components of air?

In order for living creatures to survive, air is crucial. The term "air" refers to a combination of several gases. It also goes by the name atmosphere. Nitrogen, carbon dioxide, oxygen, and several more gases, all in minute quantities, are among the various gases that make up air.

Nitrogen is the most abundant gas and its concentration is $78\%$. It is represented with a symbol $\mathrm{N}$ and its atomic number is $7$.

Nitrogen is found in almost all living organisms in the form of amino acids and nucleic acid.

Oxygen is the most important element of air and its concentration is $21\%$. It is represented with a symbol $\mathrm{O}$ and its atomic number is $8$.

Oxygen is essential for breathing and respiration.

The concentration of carbon dioxide is found to be $0.04\%$. It is represented with a symbol ${\mathrm{CO}}_2$.

It is a trace gas but its amount is highly increasing due to air pollution because of various activities such as deforestation and industrialization.

Hence, option A is correct.