Which horizon is commonly referred to as subsoil; lighter layer below topsoil, mostly minerals with little to no organic matter?

• A. B Horizon
• B. O Horizon
• C. A Horizon
• D. C Horizon

Answer: (A)

The main idea here is identifying which soil layer is called subsoil by its makeup and position. Subsoil is the mineral-rich layer beneath the topsoil that has received materials leached down from above (illuviation). It typically contains little organic matter compared with the surface layer, so it often appears lighter in color and is dominated by minerals rather than organic material.

This description matches the B horizon, which sits below the topsoil and is characterized by accumulated minerals such as clay and oxides from the layers above. The O horizon is the organic surface layer, the A horizon is the organic-rich topsoil, and the C horizon is the less-weathered parent material.