Which of the following actions is not permissible while in uniform?

The action of walking while eating is generally considered permissible in uniform, as long as it does not interfere with military decorum or safety. Service members are often required to fulfill their duties in a timely manner, and in situations where time is limited, it may be practical to eat while walking. However, it's essential to maintain professionalism while in uniform.

Wearing unauthorized accessories is explicitly not permissible as it violates military regulations regarding proper uniform appearance and standards. These regulations are put in place to ensure uniformity and discipline among service members. Unauthorized items can detract from the professional appearance that uniforms are intended to represent.

Eating without permission is also typically not allowed in certain formal settings or situations, as it may not align with proper conduct expected of military personnel. In specific contexts, especially during formal events or ceremonies, service members may need to wait for permission to eat or drink.

Participating in military drills is always expected behavior while in uniform, as it reflects a service member's commitment to their duties and preparedness.

In summary, while walking and eating may not violate any explicit rules, it is essential to maintain overall decorum and the expectations of military service, making other actions like wearing unauthorized accessories clearly outside the bounds of permissible behavior.