It is difficult to estimate when cyanobacteria appeared on Earth using evidence from the oxidation state of the Earths crust, because
A. several abiotic reactions could have formed Fe3+.
B. there are multiple forms of anoxygenic photosynthesis.
C. there are multiple groups of oxygenic photosynthetic bacteria.
D. several ancient anaerobic metabolisms form Fe3+.
Answer:D
It is difficult to estimate when cyanobacteria appeared on Earth using evidence from the oxidation state of the Earths crust, because
A. several abiotic reactions could have formed Fe3+. B. there are multiple forms of anoxygenic photosynthesis. C. there are multiple groups of oxygenic photosynthetic bacteria. D. several ancient anaerobic metabolisms form Fe3+.