Which stitch is characterized by being stretchy and is commonly used for knits?

The cover stitch is the correct choice for being characterized by its stretchiness and is often used for sewing knits. This type of stitch is especially beneficial for knit fabrics because it allows the seams to stretch without breaking, maintaining the integrity and fit of the garment. The cover stitch typically forms a professional-looking finish on hems and the edges of knit items, providing both strength and flexibility.

In knit sewing, the ability to stretch is crucial; this is why the cover stitch's design, which combines a straight stitch on the top and a chain stitch on the bottom, is ideal for handling the movement and elasticity of knit fabrics. Its effectiveness in allowing the garment to maintain its shape while providing durability is key for any stretchable clothing, making it a preferred choice among garment makers and tailors.