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photosynthesis
Yes
mostly carbon dioxide with little or no oxygen.
Oxygen Please study this, & don't forget it so you don't have to keep looking up answers .
on ancient Earth, nitrogen, water vapor, carbon dioxide, and methane were probably the most abundant gases in the atmosphere.
yes
oxygen
oxygen
nitrogen
nitrogen
photosynthesis
no
photosynthsis
Photosynthesis by plants
Hydrogen and helium
Carbon dioxide
it dissolved into the ocean