Answer:
soil
Step-by-step explanation:
The biggest natural carbon storage, or carbon sink, is the soil. The other two major natural carbon sinks are the ocean waters and the living organisms (mainly the plants). The storage of carbon is basically a process through which the carbon is trapped and removed from the atmosphere on a longer period of time, thus it is not active in the carbon cycle temporarily. The storage of carbon happens through biological, chemical, and physical process, and the soil gets and traps the carbon through all of them. A problem occurs in the past couple of centuries because there is more and more soil that has been damaged or destroyed, thus lot of carbon has been released into the atmosphere, and the soil has lesser capacity for taking in new carbon in it.