Q. Consider the following: 1. Photosynthesis 2. Respiration 3. Decay of organic matter 4. Volcanic actionWhich of the above add carbon dioxide to the carbon cycle on Earth? 

1. 1 and 4 only
2. 2, 3 and 4 only
3. 2 and 3 only
4. 1, 2, 3 and 4