What part of a rabbit's fur is described as the base of the fur shaft, adjacent to the skin?

The correct choice is the term that refers to the part of the rabbit's fur closest to the skin, which is commonly known as the underfur. The underfur is softer and finer compared to guard hairs and provides insulation and warmth for the rabbit. Understanding the structure of rabbit fur is crucial for various aspects of rabbit care, including grooming and assessing the health of the animal. The other terms do not accurately represent the part of the fur adjacent to the skin; guard hairs are the coarser outer layer that protects the underfur, belly fur refers to the fur on the rabbit's underside, and color describes the visual appearance of the fur rather than its structural properties.