Answer:
A) The presence of iron oxides (rust) in sedimentary rock layers that are 2 billion years old
Explanation:
Cyanobacteria learned aerobic photosynthesis. As a result, they absorbed CO2 and solar energy to break down water molecules, releasing oxygen into the atmosphere. This was how oxygen came to planet earth and allowed the life we know.
The strong oxidizing power of oxygen has transformed iron into iron oxide that is deposited on the seabed in layers. Once saturated minerals, oxygen begins to accumulate in the atmosphere.
Thus, we can say that the evidence of the participation of cyanobacteria in the release of oxygen in our atmosphere is the presence of iron oxides (rust) in 2 billion year old sedimentary rock layers.
