Written by Merel Dagher (PEACE Advisor) 

Which of the following was responsible for initially creating an oxygen-rich environment?

a.     cyanobacteria

b.     fungi

c.     algae

d.     protists

e.     bryophytes


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The correct answer is a. Thanks to the photosynthetic activity of cyanobacteria, the atmosphere eventually accumulated levels of oxygen (oxygen is a product of photosynthesis, along with sugar). Cyanobacteria also make up biofuels (not algae).

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