A moistened soil sample which can be moulded to form a smooth continuous ring is characteristic of

A moistened soil sample that can be moulded into a smooth continuous ring is a characteristic of a soil with a significant clay content. This is because soils with higher clay content have the ability to hold water and maintain soil structure even when moistened. Clay particles are very small and have a large surface area, so they can hold a lot of water and nutrients. Therefore, a soil with a high clay content will feel sticky when wet and can be easily moulded, indicating its cohesive properties. So, the correct option is heavy clay.