Final answer:
Ultralu is a fabric often used in activewear and is best suited for yoga because of its stretchy and comfortable nature, which is ideal for flexibility exercises.
Step-by-step explanation:
Ultralu is a fabric commonly associated with activewear, primarily designed for activities that demand flexibility and comfort. When considering the choices listed, Ultralu is best suited for yoga, which is a flexibility exercise. Yoga practices focus on stretching and improving the range of motion of muscles and joints, and consistent stretching is vital for avoiding activity-related injuries. While Ultralu might be worn for a variety of physical activities, it is especially ideal for yoga due to the material's stretch and comfort properties.