AP Environmental Science

Answer: D - You would find humus in the A horizon.

Key Takeaway: When soil is formed, differences in texture, color, structure, and composition change depending upon the soil’s depth. These differences split the soil into different layers, known as horizons. The O and A horizons make up the top soil. The O horizon is comprised of organic material that is decaying, such as leaf litter or compost. The A horizon is humus mixed with minerals.