How does clay soil typically behave?

Clay soil is characterized by its fine particles, which are less than 0.002 mm in diameter. This small particle size contributes to its high plasticity and stickiness when wet. During wet conditions, clay soil has the ability to hold significant amounts of moisture, resulting in a malleable texture that allows it to be easily shaped and manipulated. This plastic nature allows it to be formed into casts without crumbling, distinguishing it from soils with larger particles, such as sand.

When clay is dry, it often hardens and can crack, but when wet, its stickiness and cohesiveness become prominent. This property is what defines its behavior and usability, especially in construction and agriculture, where understanding soil mechanics is crucial.

In contrast, the other options describe behaviors that do not align with the intrinsic characteristics of clay soil. For instance, a weak cast that crumbles would relate more to sandy or silty soils that do not have the cohesive properties of clay. A loose, non-sticky texture is characteristic of sandy soils with larger particles, while slight staining of fingers is not a notable feature of clay, which tends to leave a more noticeable residue when handled.