Which of the following describes the importance of cyanobacteria to early Earth atmospheric formation?

A) cyanobacteria released oxygen into the air, creating a protective ozone layer

B) cyanobacteria released nitrogen into the air, creating a protective ozone layer

C) cyanobacteria absorbed excess oxygen from the air, creating proper amounts of atmospheric oxygen

D) cyanobacteria absorbed excess carbon dioxide from the air, creating a protective ozone layer