Final answer:
Silk is the correct answer as it is a strong, lustrous, medium to heavyweight fabric made of spun yarn in a satin weave, known for its unique shimmer due to the fiber's triangular prism-like structure.
Step-by-step explanation:
The fabric that is strong, lustrous, medium to heavyweight, and made of spun yarn in a satin weave is silk. This luxurious fabric has a rich history and has been highly valued across cultures for thousands of years. Silk is derived from the cocoons of the silkworm, which are unwound into thin strands that are combined to create a strong thread.
The unique triangular prism-like structure of the silk fiber refracts light, giving the fabric its characteristic shimmer. Satin, on the other hand, refers to the weave of the fabric rather than the fiber and can be made from silk or synthetic fibers like polyester, which can also be satiny in appearance but differ in properties.