Detritivores breakdown detritus into smaller particles. The process is called :
Fragmentation
Humification
Decomposition
Catabolism
Humification Accumulation of Humus
Decomposition Breakdown of bigger substances into simpler parts especially by the action of living things
Catabolism Degradation of detritus into simple inorganic substances by bacterial and fungal enzymes.
Fragmentation Breakdown of detritus by detritivores
Hence option 1 is correct.