Final answer:
The oceans are the largest carbon pool in the slow part of the carbon cycle, storing more carbon than fossil fuels, soil, and the atmosphere.
Step-by-step explanation:
The largest carbon pool in the slow part of the carbon cycle is found in the oceans. The oceans act as major carbon reservoirs, where carbon is stored for long periods in the form of dissolved inorganic carbon, carbonates, and organic materials. Sedimentary rocks, including fossil fuels, are also significant pools of carbon and can store carbon for millions of years, but the amounts found in oceans surpass those in fossil fuels. On land, carbon is also stored in soil as organic carbon due to decomposition and weathering processes. However, the ocean sediments and water contain the most substantial amount of carbon in the slow carbon cycle, much more than in the atmosphere or soil.