On which of the following uniforms are ribbons and aiguillettes not authorized?

The correct uniform on which ribbons and aiguillettes are not authorized is the Physical Training Uniform. This uniform is specifically designed for physical activities and athletic training, focusing on comfort and practicality rather than formalities like ribbons and aiguillettes which represent achievements and rank insignia. Ribbons, which denote awards or accomplishments, and aiguillettes, which are decorative cords indicating specific positions or honors, are elements associated with more formal uniforms that signify military tradition and protocol.

In other uniforms like Winter Working Blue, Service Dress Blue, and Summer Whites, it is standard practice to wear ribbons and aiguillettes as they serve to indicate the wearer's qualifications, medals, and service honors, aligning with the formal appearance expected in those settings. Thus, the Physical Training Uniform stands out as the exception where these items are not worn, allowing for unencumbered movement and comfort during physical training exercises.