What distinguishes clay from sand and silt in terms of soil composition?

Clay is distinguished from sand and silt primarily due to its unique particle size and surface area characteristics. Clay particles are notably smaller than those of sand and silt, leading to a greater surface area per unit volume. This larger surface area allows clay to retain more water and nutrients, which is crucial for soil fertility and plant growth.

The structure and small size of clay particles also contribute to their ability to form aggregates and influence the physical properties of the soil, such as aeration and drainage. In contrast, sand has larger particles and a considerably lower surface area, making it less effective in retaining moisture and nutrients.

The chemical activity of clay is another distinguishing factor, but the correct option emphasizes the importance of surface area, which plays a significant role in soil behavior. Therefore, identifying clay by its large surface area per volume is a key differentiator in soil composition.