Permeability refers to the ability of a material, such as soil, to allow fluids or gases to pass through it. The permeability of soil is influenced by several factors, including grain size, void ratio, and the structural arrangement of soil particles.

Grain Size:
- The size of soil particles has a significant impact on permeability. Coarse-grained soils, such as sand and gravel, typically have higher permeability compared to fine-grained soils, such as silt and clay.
- This is because the larger spaces between the particles allow water to flow more easily, increasing the permeability. In contrast, fine-grained soils have smaller particle sizes and more compacted structures, resulting in lower permeability.

Void Ratio:
- The void ratio of soil refers to the ratio of the volume of voids (empty spaces) to the volume of solids in a given sample of soil.
- A higher void ratio indicates a greater volume of voids, which means there is more space for water or other fluids to flow through the soil.
- Therefore, soils with higher void ratios tend to have higher permeability, as there is more room for fluid movement.

Structural Arrangement of Soil Particles:
- The way soil particles are arranged and packed together also affects permeability.
- Well-graded soils with a more uniform distribution of particle sizes tend to have higher permeability compared to poorly graded soils with uneven particle distribution.
- Well-graded soils have a more open and interconnected structure, allowing fluids to flow more easily through the soil.
- In contrast, poorly graded soils have a more compacted structure with limited pathways for fluid flow, resulting in lower permeability.

Overall, the permeability of soil is influenced by a combination of these factors. Grain size, void ratio, and the structural arrangement of soil particles all play a role in determining how easily fluids can pass through the soil. Therefore, the correct answer is option 'D' - all of the above.