Which of the following repairs specifically requires sewing?

Sewing is an essential method of repair for cotton fabric due to the nature and structure of the material. Cotton fabric has properties that benefit from the secure and durable attachment that sewing provides, especially in areas that might experience stress or strain. This is particularly important in the realm of aircraft fabric covering, where maintaining integrity in the fabric is crucial for safety and performance.

While polyester and nylon fabrics may also require maintenance, they are often repaired using heat-sealing techniques or adhesive methods which are more suited to their characteristics. Fabric patches can be applied to various types of fabric and may not necessarily require sewing if appropriate adhesives or heat processes are used. However, when dealing with cotton, sewing ensures a robust and long-lasting repair that aligns with standard practices in aircraft maintenance.