Through which of the following processes does carbon enter the atmosphere?

• A. Photosynthesis in plants
• B. Absorption by ocean water
• C. Respiration by living organisms
• D. Formation of fossil fuels

Answer: (C)

Verified step by step guidance

1. Step 1: Begin by understanding the carbon cycle, which describes how carbon moves through the Earth's biosphere, atmosphere, hydrosphere, and geosphere. Carbon enters the atmosphere primarily as carbon dioxide (CO₂).
2. Step 2: Analyze each process mentioned in the problem to determine whether it contributes to carbon entering the atmosphere. For example, photosynthesis in plants removes CO₂ from the atmosphere, so it does not contribute to carbon entering the atmosphere.
3. Step 3: Consider the process of absorption by ocean water. This process involves CO₂ being dissolved into the ocean, which removes carbon from the atmosphere rather than adding it.
4. Step 4: Evaluate respiration by living organisms. During cellular respiration, organisms break down glucose (C₆H₁₂O₆) to produce energy, releasing CO₂ as a byproduct. This process directly contributes to carbon entering the atmosphere.
5. Step 5: Examine the formation of fossil fuels. This process involves the long-term storage of carbon in the Earth's crust, which does not release carbon into the atmosphere. Therefore, it does not contribute to carbon entering the atmosphere.