Match the following columns
`{:("","Column-I","",Column-II),(A,"O-horizon",1,"surface layer of organic matter"),(B,"A-horizon",2,"upper most soil called top soil"),(C,"B-horizon",3,"sub-soil"),(D,"C-horizon",4,"irregular rock fragments"):}`

Options

A. `{:(A,B,C,D),(4,3,2,1):}`
B. `{:(A,B,C,D),(4,3,1,2):}`
C. `{:(A,B,C,D),(1,2,3,4):}`
D. `{:(A,B,C,D),(1,2,4,3):}`

Answer

To solve the question of matching the soil horizons from Column-I with their corresponding descriptions in Column-II, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Horizons**:
- The horizons listed in Column-I are:
- A: O-horizon
- B: A-horizon
- C: B-horizon
- D: C-horizon

2. **Understand Each Horizon**:
- **O-horizon**: This is the organic layer rich in decomposed organic matter (humus). It is often considered above the true soil.
- **A-horizon**: Known as the topsoil, this layer is where most biological activity occurs and contains a mix of organic material and minerals.
- **B-horizon**: This is the subsoil, which has less biological activity and is primarily composed of minerals leached from the upper layers.
- **C-horizon**: This layer consists of weathered rock fragments and has minimal biological activity.

3. **Match Each Horizon with Its Description**:
- **O-horizon** matches with **1**: "surface layer of organic matter".
- **A-horizon** matches with **2**: "upper most soil called top soil".
- **B-horizon** matches with **3**: "sub-soil".
- **C-horizon** matches with **4**: "irregular rock fragments".

4. **Final Matching**:
- A (O-horizon) → 1 (surface layer of organic matter)
- B (A-horizon) → 2 (upper most soil called top soil)
- C (B-horizon) → 3 (sub-soil)
- D (C-horizon) → 4 (irregular rock fragments)

### Final Answer:
- The correct matches are:
- A → 1
- B → 2
- C → 3
- D → 4