Q: 48 (IAS/2011)

Consider the following
1. Photosynthesis
2. Respiration
3. Decay of organic matter
4. Volcanic action
Which of the above add carbon dioxide to the carbon cycle on Earth ?
question_subject: 
Ecology
question_year: 
2011
question_exam: 
IAS
question_sub_subject: 
Ecology
question_topic: 
Ecology
stats: 
0,9160,3272,296,424,9160,2552