It Is Difficult to Estimate When Cyanobacteria Appeared on Earth

question 81

Multiple Choice

It is difficult to estimate when cyanobacteria appeared on Earth using evidence from the oxidation state of the Earth's 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⁺.

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