Which of the following adds/add carbon dioxide to the carbon cycle on the planet Earth?

1. Volcanic action
2. Respiration
3. Photosynthesis
4. Decay of organic matter

Select the correct answer using the code given below.

[UPSC Civil Services Exam – 2014 Prelims]

(a) 1 and 3 only

(b) 2 only

(c) 1, 2 and 4 only

(d) 1, 2, 3 and 4

Answer: (c)        

Explanation:

• The process of photosynthesis absorbs carbon dioxide and releases oxygen, meaning that it does not contribute to the addition of carbon dioxide to the carbon cycle. Therefore, Statement 3 is incorrect.
• Volcanic activity results in the emission of carbon dioxide.
• Respiration involves the intake of oxygen from the external environment into tissues and the release of carbon dioxide in the opposite direction.
• Decomposition releases carbon dioxide into the atmosphere.