How should a Soldier's mustache be maintained according to regulation?

A Soldier's mustache should be maintained in a manner that is neat and tidy, reflecting the standards of military appearance and professionalism. This means that the mustache should be trimmed regularly to ensure it does not extend beyond the corners of the mouth and remains well-groomed. Maintaining a neat mustache is important for several reasons, including promoting uniformity among service members, respecting the military's code of conduct, and presenting a disciplined image.

The other choices highlight behaviors that are not in alignment with military grooming standards. Allowing a mustache to grow wild without trimming can create an unkempt appearance, while styling with designs is typically not permissible as they deviate from standard grooming regulations. Likewise, extending the mustache below the chin line contradicts the requirement for a properly maintained facial hair style in the military context. Thus, the emphasis on a neatly trimmed and tidy appearance reflects the values upheld by military regulations.