What type of material can be identified by observing soil that remains in clumps when excavated?

The correct choice highlights that cohesive material is defined by its ability to stick together, forming clumps or clods when excavated. This characteristic is primarily due to the fine particles contained within cohesive soils, such as clay, which have strong interparticle forces, allowing them to maintain their structure despite being disturbed. Cohesive soils typically exhibit this property when wet, allowing them to hold their shape and be easily molded.

In contrast, granular materials, such as sand and gravel, do not retain their shape when disturbed and tend to fall apart into loose particles. They lack the fine particles and binding properties that cohesive soils possess. Mixed materials can include a combination of both cohesive and granular particles, but the question specifically refers to the behavior of the soil when excavated, which aligns with cohesive materials. Loose materials also do not hold together well and will not clump when excavated, reinforcing that cohesive materials are the correct identification in this context.