The correct answer is A. 18.6 kN/m3.
The dry density of soil is the mass of dry soil per unit volume of soil. It is calculated by dividing the dry mass of soil by the total volume of soil. The total volume of soil is equal to the bulk volume of soil minus the volume of water in the soil.
The bulk density of soil is the mass of soil per unit volume of soil. It is calculated by dividing the total mass of soil by the total volume of soil. The total volume of soil is equal to the volume of the soil particles plus the volume of water in the soil.
The water content of soil is the ratio of the mass of water in the soil to the mass of dry soil. It is expressed as a percentage.
To calculate the dry density of soil, we can use the following equation:
Dry density = Bulk density / (1 + Water content)
In this case, the bulk density is 22 kN/m3 and the water content is 10%. Therefore, the dry density of soil is:
Dry density = 22 kN/m3 / (1 + 0.1) = 18.6 kN/m3