Explanation:

- A-horizon (Option 1): Correct Answer. The A-horizon is also known as the topsoil. It is rich in organic material, including humus, formed from decayed plant and animal matter. This layer is crucial for nutrient supply and plant growth.

- C-horizon (Option 2): This layer lies beneath the B-horizon. It contains partially broken-down rock but lacks significant amounts of organic material and humus.

- Bedrock (Option 3): This is the bottom layer of soil, composed of continuous rock. It does not contain humus because it is solid rock without organic content.

- B-horizon (Option 4): Known as subsoil, this layer contains minerals leached from the A-horizon but has less organic material or humus compared to the topsoil.