ANS:E - clays.

1. Particle Size: Clay particles are the smallest among the three main soil types (sand, silt, and clay). They are so small that they cannot be seen with the naked eye and require a microscope to be observed individually.
2. Mineral Composition: Clays are predominantly composed of various hydrated aluminum silicates, such as kaolinite, illite, and montmorillonite. These minerals give clay its characteristic plasticity and cohesive behavior.
3. Plasticity: One of the defining characteristics of clay is its plasticity, which refers to its ability to be molded and shaped without breaking. When moistened, clay soils can be easily molded into various shapes. This property makes clay an essential material in pottery and ceramics.
4. Cohesiveness: Clay particles have a strong tendency to stick together due to electrostatic forces and water films surrounding the particles. This cohesion gives clay its characteristic strength and stability when moistened.
5. Hydraulic Conductivity: Clay soils have very low hydraulic conductivity, meaning they have poor drainage and water movement properties. This is because the small particle size and high cohesion of clay particles restrict the flow of water through the soil.
6. Shrink-Swell Behavior: Clay soils are prone to significant volume changes with changes in moisture content. They tend to shrink when dry and swell when wet. This shrink-swell behavior can lead to cracking and structural problems in buildings and infrastructure built on clay soils.
7. Fertility: Clay soils are often fertile due to their high nutrient-holding capacity. The small particle size and high surface area of clay particles allow them to retain nutrients and make them available to plants.