Answer :
Answer:
A) The presence of iron oxides (rust) in sedimentary rock layers that are 2 billion years old.
Explanation:
- Cyanobacteria are aquatic and photosynthetic ,they live in water and manufacture own food releasing oxygen as a by product and in which most living organisms depend on.
- Cyanobacteria are found in the ocean and are believed to be responsible for the formation of the iron oxide found on the sedimentary rocks since they release oxygen as a by product and it is used in the iron oxide formation process below the level of wave disturbance.
Answer:
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.