Final answer:
The Loess Bluffs region is characterized by loose, windblown soil, which is fertile for agriculture but prone to wind erosion if not properly managed.
Step-by-step explanation:
The geographic feature of the Loess Bluffs region is D. loose, windblown soil. Loess is fine silt or clay-like material, yellowish in color due to its composition, that is deposited by the wind. This type of soil is fertile and conducive to agriculture when stabilized but is susceptible to erosion when the vegetative cover is removed or the land is overcultivated. An example of the environmental vulnerability of this soil is the Dust Bowl, where extensive farming and drought led to massive soil erosion due to the winds blowing the topsoil away.