Carbon (ii) oxide(carbon monoxide)
carbon (iv) oxide ( carbon dioxide)
oxide of sulfur and nitrogen
water vapor soot.
Gases expand<span> as heat is put into a </span>gas<span> the molecules gain energy and move faster and faster.</span>
It means , one , only , single .. hopes this helps
Easy. Answer is oxygen because it says which one was missing before any life was on earth. And in order to have life on earth you need oxygen!
:)