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.
(a) 1 and 3 only (b) 2 only (c) 1, 2 and 4 only (d) 1, 2, 3 and 4
