Which one of the following processes during decomposition is correctly described?

Options

A. Catabolism - Last step in the decomposition under fully anaerobic condition
B. Leaching - Water soluble inorganic nutrients rise to the top layers of soil
C. Fragmentation - Carried out by organism such as earthworm
D. Humification - Leads to the accumulation of a dark coloured substance humus which undergoes microbial action at a very fast rate

Explanation

**Step-by-Step Solution:**

1. **Understanding Decomposition:**
- Decomposition is the process of breaking down complex organic matter into simpler inorganic matter. It is crucial for nutrient cycling in ecosystems.

2. **Identifying the Steps of Decomposition:**
- There are five main steps in the decomposition process:
1. **Fragmentation**: The breaking down of detritus into smaller pieces by detritivores (organisms that feed on dead organic matter).
2. **Leaching**: The process where nutrients are released into water and move down into the soil.
3. **Catabolism**: The breakdown of complex molecules into simpler molecules.
4. **Humification**: The formation of dark-colored humus in the soil, which occurs at a slow rate.
5. **Mineralization**: The degradation of humus to release inorganic nutrients.

3. **Evaluating the Options:**
- **Option A**: Claims that catabolism is the last step under fully anaerobic conditions. This is incorrect; catabolism is the third step, not the last.
- **Option B**: States that leaching causes water-soluble inorganic nutrients to rise to the top layer of the soil. This is also incorrect; leaching causes nutrients to move down into the soil.
- **Option C**: States that fragmentation is carried out by organisms such as earthworms. This is correct, as earthworms are indeed detritivores that aid in fragmentation.
- **Option D**: Claims that humification leads to the accumulation of humus through microbial action at a fast rate. This is incorrect; humification occurs slowly and does not primarily involve microbial action.

4. **Conclusion:**
- The only correct description of a process during decomposition is **Option C**, which accurately describes fragmentation carried out by organisms like earthworms.