Alfisols are the type of soil described, being well-developed, rich in nutrients due to the organic matter from leaf litter, and found in the temperate regions of the central United States.
The question is concerned with identifying a type of soil that is moderately leached, has high fertility, contains a subsurface horizon of accumulated clay, and is typically found in temperate humid and subhumid regions like the central part of the US. Given the characteristics mentioned, the final answer in two lines would be: c) Alfisols. These soils are well-developed, rich in nutrients because of the decomposition of leaf litter, and are characteristic of areas with distinct seasonal climates where deciduous trees dominate.
They also have the B horizon where clay accumulates, which fits the description provided in the question.
So, Alfisols are commonly found in temperate regions and have a subsurface accumulation of clay. They support a temperate deciduous forest environment thanks to their high fertility levels which are maintained by the seasonal decomposition of vegetation that contributes organic matter to the soil, making them highly productive for agricultural purposes, particularly in the central part of the United States.