Answer: C. O horizon
Soil profile is made up of different types of soil horizons. Soil horizons refers to the distinct layers of soils which are parallel to the earth crust. These horizons are distinct from each other on the basis of properties like texture, color, amount of organic matter present and amount of mineral elements present.
The O horizon is the top layer of soil that composed of partially decomposed materials like leaves, plants and animal remains. This layer is thinnest as compared to other horizons. It exhibit dark color soil because of the presence of the organic matter.
