Which of the following adds/add carbon dioxide to the carbon cycle on the planet Earth?
- Volcanic action 2. Respiration 3. Photosynthesis 4. Decay of organic matter
Select the correct answer using the code given below.
(a) 1 and 3 only (b) 2 only (c) 1, 2 and 4 only (d) 1, 2, 3 and 4