Which soil type can form a flexible ribbon more than 3 inches long?

The ability of a soil type to form a flexible ribbon more than 3 inches long is primarily associated with high clay content. Clay particles are very small and have a plate-like structure, which allows them to stick together and create a cohesive mass when moist. This characteristic makes clay soils highly plastic and capable of forming long ribbons during the ribbon test, which is a simple method to determine soil texture.

When performing the ribbon test, clay can stretch significantly due to its fine texture and moisture retention properties. This flexibility and potential for elongation are fundamentally due to the way clay particles interact with water and with each other, allowing for the development of a long, pliable ribbon. In contrast, other soil types like silty clay loam, loam, and loamy sand typically lack sufficient clay content to achieve such length in their ribbon formation, as they contain a higher proportion of larger particles or mixed textures that do not exhibit the same plasticity.

Thus, the correct answer stems from understanding the intrinsic properties of clay and its ability to form long, flexible ribbons under the right moisture conditions.