Final answer:
The serged seam is the most suitable for stretchy fabrics, providing durability and flexibility, making it a go-to choice for activewear and similar garments.
Step-by-step explanation:
The type of seam that works best for stretchy fabrics is the serged seam. This seam type uses an overlock stitch that not only finishes the edge but also allows for the fabric to stretch without breaking the stitches. Serged seams are commonly used in the construction of activewear, lingerie, and other garments made from stretchy materials because they provide strong, stretchy, and professional-looking finishes that can endure the fabric's movement.