Correct Option
The carbon cycle involves the exchange of carbon among the atmosphere, oceans, land, and living organisms. Processes that add carbon dioxide (CO₂) to the atmosphere include:
- Volcanic action: Volcanic eruptions release significant amounts of CO₂ into the atmosphere, originating from the Earth's interior. This is a natural geological process contributing to the atmospheric carbon pool.
- Respiration: Cellular respiration, carried out by living organisms (plants, animals, microbes), involves the breakdown of organic compounds to release energy. CO₂ is produced as a byproduct and released into the atmosphere or water.
- Decay of organic matter: The decomposition of dead organic matter (plants and animals) by microorganisms (bacteria and fungi) releases carbon, primarily as CO₂, back into the atmosphere and soil. This process is a crucial part of the carbon cycle.
Photosynthesis (Point 3) is a process that removes CO₂ from the atmosphere, rather than adding it. Green plants, algae, and some bacteria absorb atmospheric CO₂ to synthesize organic compounds, thereby fixing carbon.
Incorrect Options
- Option (A) is incorrect because it includes photosynthesis, which removes CO₂ from the atmosphere.
- Option (B) is incomplete as it only accounts for respiration and omits volcanic action and decay of organic matter, both of which add CO₂.
- Option (D) is incorrect because it includes photosynthesis, which is a process that consumes atmospheric CO₂, not releases it.