From the TOP TO BOTTOM it is tertiary 1
secondary 10
primary 90
Producers 100
Explanation:
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!
:)
C........................................................................................................
"Benzaldehyde is an organic compound consisting of a benzene ring with a formyl substituent. It is the simplest aromatic aldehyde and one of the most industrially useful. It is a colorless liquid with a characteristic almond-like odor."
https://www.britannica.com/science/benzaldehyde
https://en.wikipedia.org/wiki/Benzaldehyde