Arrange the following steps involved in decomposition of detritus in…

The correct answer is Option (4) → (D), (B), (C), (A)

(D) Fragmentation — this comes first. Detritivores such as earthworms break the detritus (dead leaves, bark, animal remains) into smaller particles. This gives more surface for the later steps.

(B) Leaching — this comes second. Water carries the water-soluble inorganic nutrients down into the soil, where they get precipitated as unavailable salts.

(C) Catabolism — this comes third. Enzymes of bacteria and fungi break the detritus into simpler inorganic substances.

(A) Humification — this comes last of the four. It builds up humus, a dark, amorphous substance that resists microbes and breaks down very slowly. Humus is a store of nutrients.

Note: A similar question was also asked in CUET (UG) 2026 on 31-05-2026 (Slot 2) and on 19-05-2026 (Slot 2), and in CUET (UG) 2023 on 08-06-2023 (Slot 3).

NCERT Extract:
Decomposition – “… The important steps in the process of decomposition are fragmentation, leaching, catabolism, humification and mineralisation. Detritivores (e.g., earthworm) break down detritus into smaller particles. This process is called fragmentation. By the process of leaching, watersoluble inorganic nutrients go down into the soil horizon and get precipitated as unavailable salts. Bacterial and fungal enzymes degrade detritus into simpler inorganic substances. This process is called as catabolism.”