What is a common technique for keeping fabric from stretching?

Applying interfacing is an effective technique for preventing fabric from stretching. Interfacing is a material added to the fabric, usually on the wrong side, to provide structure and stability. It reinforces specific areas, such as collars, cuffs, and waistbands, to help them maintain their shape and resist distortion during wear and washing. This is particularly important for garments where precision and fit are crucial.

In contrast, using lighter weight fabrics, cutting on the bias, and making alterations do not primarily address the issue of stretching. Lighter fabrics may not have the same weight and structure, which could lead to a tendency to stretch. Cutting on the bias allows for more flexibility and drape in the fabric, potentially making it more prone to stretching rather than preventing it. Making alterations typically focuses on fit rather than the inherent qualities of the fabric itself concerning stretch prevention. Hence, applying interfacing is the most direct and effective method among the choices provided.