D. Biological activity
Explanation:
The earth's atmosphere became oxygen rich as a result of biological activities. Early earth atmosphere was toxic one and in its reducing state.
- The activities of micro-organisms such as cyanobacteria led to the production of oxygen.
- These organisms manufacture their food in the presence of sunlight and water in the process of photosynthesis.
- The bye product of this reaction is oxygen.
- The intense presence of these living organisms led to the surge in atmospheric oxygen.
Learn more:
Photosynthesis brainly.com/question/4216541
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Answer:
Hello There!!
Explanation:
The last option is the answer. A behavior that helps an organism camouflage.
hope this helps,have a great day!!
~Pinky~
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