Answer:
4. The carbon in the ocean circulates through the water and is released by anaerobic respiration.
Explanation:
Carbon cycle involves the transfer of carbon between the atmosphere (air) hydrosphere (water), biosphere (living organisms) etc. Carbon in form of carbon dioxide enters into water bodies e.g ocean via diffusion, which is used by aquatic plants for photosynthesis.
The carbon dioxide is then released when some set of living organisms undergo anaerobic respiration. Hence, carbon in the ocean circulates through the water and is eventually released into the atmosphere when organisms undergo respiration.