Which of the following types of soil has high permeability?

Gravel is characterized by its large particle size and structure, which allows water to flow through it freely. This high permeability makes gravel an ideal material for drainage systems and construction applications where effective water movement is crucial. The spaces between the larger gravel particles can be quite significant, promoting rapid water drainage and reducing the likelihood of water retention.

In contrast, clay has very small particles that are tightly packed together, leading to low permeability as water struggles to pass through. Silt, while more permeable than clay, still does not match the permeability of gravel due to its finer texture. Sand strikes a balance, with higher permeability than clay and silt; however, it cannot achieve the exceptional drainage properties of gravel. Thus, gravel is recognized for its superior permeability compared to other soil types, making it the correct answer in this context.