What is the term for the wool covering of sheep?

The correct term for the wool covering of sheep is "fleece." Fleece refers specifically to the soft, woolly coat that sheep develop as a natural protective layer. This fleece is composed of fibers that can be sheared and processed for various uses, including clothing and textiles.

In the context of animal coverings, "pelage" describes the fur of mammals in general, encompassing a wide range of fur types across different species. "Undercoat" refers specifically to the dense layer of soft hair found beneath the guard hairs in certain animals, providing insulation. "Fiber" is a broader term that can describe any filament or thread-like structure, including those from plants or animals, but does not specifically refer to the covering of sheep. The definition and specificity of fleece make it the correct choice in this case.