Which of the following processes removes carbon from the atmosphere?

Step 1: Analyze the question The question asks which process removes carbon (as carbon dioxide) from the atmosphere. We need to find the process that takes carbon out of the air, not one that puts it in.

Step 2: Explain the concept (the carbon cycle) Carbon moves between the atmosphere, living things, soil, and the oceans.

• Processes that add CO₂ to the atmosphere: respiration, decay/putrefaction, burning (combustion) of fuels, and volcanic eruptions.
• Processes that remove CO₂ from the atmosphere: photosynthesis (and dissolving of CO₂ in oceans).

During photosynthesis, green plants take in CO₂ from the air and use light energy to make glucose:

6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂ (in the presence of light and chlorophyll)

Step 3: Check each option

• A. Putrefaction: This is the decay of dead organisms by bacteria. It releases CO₂ into the air, so it adds carbon.
• B. Photosynthesis: Plants absorb CO₂ and convert it to carbohydrates, so it removes carbon from the atmosphere. ✔
• C. Volcanic eruption: It releases CO₂ and other gases, so it adds carbon.
• D. Burning of fuels: Combustion of coal, petrol, wood, and so on releases CO₂, so it adds carbon.

Step 4: Answer The correct answer is B. photosynthesis.

Exam tip: For carbon cycle questions, remember that photosynthesis is the "carbon sink", while respiration, decay, combustion, and volcanoes are the "carbon sources". If the question asks about removing CO₂, think of plants. If it asks about adding CO₂, think of the other processes.