the first major source of oxygen gas was _____.\n○ cyanobacteria\n○ banded iron formations\n○ volcanic…

the first major source of oxygen gas was _____.\n○ cyanobacteria\n○ banded iron formations\n○ volcanic outgassing\n○ meteorite impacts

the first major source of oxygen gas was _____.\n○ cyanobacteria\n○ banded iron formations\n○ volcanic outgassing\n○ meteorite impacts

Answer

Brief Explanations:

Cyanobacteria were the first to perform oxygen - producing photosynthesis, releasing oxygen into the atmosphere.

Answer:

cyanobacteria