When is it permissible to wear a cover indoors?

Wearing a cover indoors is permissible specifically when an individual is under arms or during ceremonial events. This is based on military customs and traditions, which dictate that service members maintain certain standards of appearance and respect for their uniform. The act of wearing a cover inside in these scenarios symbolizes readiness, respect, and adherence to military protocols.

In ceremonial contexts, wearing a cover indoors aligns with established practices meant to honor the significance of the event. During times when personnel are under arms, it demonstrates a continued state of readiness and professionalism.

The other options involve situations that do not align with military customs regarding indoor cover wear. For example, formal dinners or being on duty may not necessarily permit wearing a cover indoors unless specified as part of a higher authority directive or specific military regulation, which is not generally the case.