Answer:
The constant gas in the atmosphere is oxygen
Explanation:
Oxygen is what allows the maintenance of life in this planet, therefore, it is the constant and needed gas in the atmosphere. Ozone is present and should be present in the highest layers of the atmosphere. Carbon dioxide is also present in the atmosphere due to the carbon cycle. Nitrogen oxide should not be in the atmosphere. The reason why carbon dioxide, ozone and nitrogen oxide are constantly found in the atmosphere is due to air pollution.
