The correct answer is: A. podsolosation
Podsols are soils that form in cool, humid climates with coniferous forests. They are characterized by a thick, leached A horizon that is low in organic matter and nutrients, and a spodic horizon that is rich in aluminum and iron oxides. The spodic horizon is often white or gray in color and composed of silica sand.
Calcification is the process of accumulation of calcium carbonate in the soil. It occurs in areas with a high pH and low rainfall. The calcium carbonate can precipitate out of the soil solution or be deposited by organisms such as snails and earthworms.
Laterization is the process of formation of laterite, a type of soil rich in iron and aluminum oxides. It occurs in tropical and subtropical climates with high rainfall and intense weathering. The iron and aluminum oxides are leached from the upper layers of the soil and deposited in the lower layers.
Gleization is the process of formation of gley soils, which are soils that are saturated with water for long periods of time. It occurs in cool, humid climates with poor drainage. The gley soils are characterized by a dark, anaerobic A horizon and a mottled B horizon.
In conclusion, the process that creates a sub layer, which is white to gray in colour and composes of silica sand in the A horizon is called podsolosation.