Answer:
1 for Human Emissions
2 for Air-Sea Gas exchange
3 for Microbial Respiration and Decomposition
(where 1 is the greatest emission and 3 is the least emission)
Step-by-step explanation:
Human Emissions consists of burning fossil fuels and producing greenhouse gasses. Cars, Coal burning factories, and such all make the human emission of carbon dioxide the greatest emission factor.
Air-sea exchange is a natural process where the ocean and the atmosphere exchange common molecules including carbon dioxide in order to balance out gases (gas-concentrations).
Microbial Respiration and Decomposition is another natural event that happens when living things breathe, decompose, etc.
Because the earth is covered with 71% of water and only about 29% land, the air-sea exchange far outnumbers microbial resp. & decomp. So, air-sea is 2 (2nd greatest factor) and microbial is 3 (least factor).