Answer:
Cyanobacteria
Step-by-step explanation:
Cyanobacteria or blue-green algae became the first microbes to produce oxygen by photosynthesis
Autotrophic Cyanobacteria.
Cyanobacteria or blue-green algae became the first microbes to produce oxygen by photosynthesis, perhaps as long ago as 3.5 billion years ago and certainly by 2.7 billion years ago.
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