Which of the following is an example of cohesive soil?

Cohesive soil is characterized by its ability to stick together due to the fine particles that compose it, which allows for the soil to maintain its shape and structure when saturated with water. Clay, as the correct answer, is a prime example of cohesive soil because it is made up of very fine particles that have a high surface area relative to volume. This allows clay particles to attract and hold water and other particles together, resulting in a cohesive material that can exhibit plasticity; it can be molded when wet and retains its form when dried.

Loam, while still a useful soil type, is a mixture of sand, silt, and clay, and doesn't demonstrate the same cohesive properties on its own that clay does. Sand is significantly coarser and composed of larger particles, making it non-cohesive as it lacks the ability to hold shape or moisture effectively when saturated. Solidified lava, on the other hand, is primarily a solid rock form and not a soil type, further distinguishing it from the properties associated with cohesive soils like clay. This distinction highlights the unique qualities of clay among soil types.