Which of the following fibers is commonly used in high-end upholstery?

Wool is commonly used in high-end upholstery due to its luxurious feel, durability, and natural ability to resist stains and soil. It has excellent resilience, making it hold its shape well and withstand the rigors of daily use, which is essential for upholstery that will be subjected to wear and tear. Additionally, wool has inherent properties such as breathability and moisture-wicking, contributing to comfort and temperature regulation in furniture.

The other fibers listed may have their own merits, but they do not typically match the overall performance and aesthetic appeal of wool in high-end applications. Acrylic, for instance, while designed to mimic wool, does not usually match its durability and natural qualities; nylon is recognized for its strength and stain resistance but is more common in commercial applications; rayon, though it has a silk-like finish, lacks the longevity and performance characteristics that are sought after in premium upholstered pieces. Therefore, wool stands out as the predominant choice for high-end upholstery.