The correct answer is: D. none of the above.
Residual soils are formed by the in situ weathering of bedrock. The weathering process can be physical, chemical, or biological. Physical weathering is the process of breaking down rocks by physical forces, such as freezing and thawing, or exfoliation. Chemical weathering is the process of breaking down rocks by chemical reactions, such as oxidation or hydrolysis. Biological weathering is the process of breaking down rocks by living organisms, such as plants and animals.
Glaciers are large masses of ice that move slowly over land. They can erode and transport soil, but they do not create soil. Wind is a powerful force that can erode and transport soil, but it does not create soil. Water is a powerful force that can erode and transport soil, but it does not create soil.
Residual soils are important because they are the parent material for many soils. They are also important because they can provide clues about the history of the landscape.