3. What is the composition of air? How is it essential to living beings?

Air is a combination of gas like nitrogen, carbon dioxide and oxygen in they are  high proportion and argon, water and other gases is small levels gas.

Explanation:

Air creates is the atmosphere pressure, air is that has it weight and mass.

The air components the nitrogen 78%, oxygen 21% and carbon dioxide 0.4%, argon 0.9% and other gases an water vapor are they small components.

plants are needed they carbon dioxide and animals need to breath the oxygen in air ,resource and available air is a natural element of nature that they are support on  earth.

Air is then equally survival like water and air is very useful animal ,plants other sources, uses air in the are follows:-(1) sustain and growth ,

(2)maintaining temperature, (3)energy supplier (4) combustion

sustain and growth :- all living things breath in the air of carbon dioxide and oxygen.

maintaining temperature :- air helps maintaining temperature on earth hot and cold air.

energy supplier :- extract energy oxygen to the energy of supplier.

combustion :- another supports of air burning or combustion.

answer(b) keep oxygenated and deoxygenated blood separate;