Explanation:

- Bacterial and fungal enzymes break down detritus into simple inorganic substances through a process called decomposition.

- Option 1: Catabolism – This refers to the general breakdown of molecules within cells, not specifically of detritus in ecosystems.

- Option 2: Fragmentation – This means breaking detritus into smaller pieces, often by physical means or by detritivores, not by enzymes.

- Option 3: Leaching – This is the loss of minerals and dissolved substances from detritus due to water, not by enzymatic action.

- Option 4: Decomposition – This is the actual process where microbes like bacteria and fungi use enzymes to break down complex organic matter into inorganic substances.

- Correct Answer: Option 4 – Decomposition