Which process is believed to have contributed to Earth's oxygen-rich atmosphere according to atomic theory?

• A. Combustion of organic matter
• B. Volcanic eruptions releasing oxygen
• C. Formation of ozone layer
• D. Photosynthesis by early cyanobacteria

Answer: (D)

Verified step by step guidance

1. Understand that the question is asking about the process that contributed to Earth's oxygen-rich atmosphere.
2. Recognize that photosynthesis is a process where organisms convert carbon dioxide and water into glucose and oxygen, using sunlight as energy.
3. Identify cyanobacteria as early photosynthetic organisms that played a crucial role in producing oxygen through photosynthesis.
4. Acknowledge that the oxygen produced by cyanobacteria accumulated in the atmosphere over time, leading to an oxygen-rich environment.
5. Conclude that photosynthesis by early cyanobacteria is the process believed to have significantly contributed to Earth's oxygen-rich atmosphere.