Which of the following soil organisms is MOST responsible for the decomposition of organic matter and the release of plant nutrients in the soil?

Bacteria and fungi are the principal decomposers of organic matter in the soil, breaking down complex organic compounds into simpler inorganic nutrients through mineralisation. While earthworms, nematodes, and millipedes contribute to physical fragmentation and mixing of organic matter, the biochemical decomposition that releases nutrients is primarily carried out by microbial organisms such as bacteria and fungi.