OSSF Designated Representative (DR) Practice Test

The correct answer highlights the major soil horizons, which are essential components in understanding soil profiles. Specifically, the soil horizons include:

- **Surface soil A (Topsoil)**: This is the uppermost layer, rich in organic matter and nutrients, and is crucial for plant growth. It is where most biological activity occurs.

- **Surface soil B (Subsoil)**: This horizon is located beneath the topsoil and often contains accumulated minerals leached from the topsoil. It may have less organic material but plays an important role in water retention and root development.

- **Parent material**: This layer consists of the unconsolidated material from which the soil develops. It can consist of weathered rock fragments and is crucial for providing essential minerals to the soil profile.

Recognizing these layers helps in understanding soil formation, fertility, and agricultural practices. The other options do not accurately represent the conventional terminology or the structure of soil horizons as recognized in soil science. For instance, “C. Subsoil, clay layer, parent material” mentions a clay layer, which is not typically identified as a separate horizon, and does not include the essential distinction between A and B horizons. Similarly, the other options either mislabel the horizons or combine unrelated concepts.