In a normal soil profile, what is the top layer called?

• A. root zone
• B. topsoil
• C. sand
• D. supersoil

Answer: (B)

The topmost layer of a normal soil profile is the topsoil, the A horizon. This layer is richer in organic matter and more biologically active than the layers beneath, which makes it the primary zone for nutrient availability and root activity. The term root zone refers to the area where most roots grow and take up water and nutrients, and it typically spans the A horizon and sometimes into the upper part of the B horizon, not just the very top layer alone. Sand describes a texture, not a named layer, and supersoil isn’t a standard soil layer term. So the correct choice is topsoil.