The correct answer is: D. fine sand.
A constant head permeameter is a device used to measure the permeability of a soil or rock. It consists of a cylindrical container filled with the soil or rock to be tested, with a porous plate at the bottom. A constant head of water is maintained above the porous plate, and the rate at which water flows through the soil or rock is measured. The permeability of the soil or rock is then calculated from the rate of water flow and the dimensions of the permeameter.
Fine sand has the highest permeability of the four options, followed by coarse sand, silt, and clay. This is because fine sand has the largest pores, which allows water to flow through it more easily. Coarse sand has smaller pores than fine sand, but larger pores than silt and clay. Silt has even smaller pores than coarse sand, and clay has the smallest pores of all.
The permeability of a soil or rock is an important property that is used in a variety of engineering applications, such as designing foundations for buildings and roads.