Which of these would be evidence that cyanobacteria evolved the ability to perform photosynthesis and released oxygen as a byproduct over 2 billion years ago? a) the presence of iron oxides (rust) in sedimentary rock layers that are 2 billion years old b) the presence of an iridium-rich layer in sedimentary rock dating from times of mass extinctions c) the presence of chloroplasts in fossilized eukaryotes from fossils dating from 2 billion years ago forward d) the formation of stromatolite rock structures from aggregates of cyanobacteria dating 3.5 billion years ago

A) The presence of iron oxides (rust) in sedimentary rock layers that are 2 billion years old.

Explanation:

Cyanobacteria perform photosynthesis using sunlight, water and carbon dioxide to produce carbohydrates as well as oxygen. In fact, to this day, all plants on Earth contain cyanobacteria - known as chloroplasts - that participate in photosynthesis. This is how oxygen arrived on earth over 2 billion years ago.

A great evidence of this moment is the presence of iron oxides (rust) in 2 billion year old sedimentary rock layers. Since it is the first report of an element that has oxygen in its composition.

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the answer will be a) proteins i believe