Which of the following best describes the authorized size of a mustache?

The authorized size of a mustache is best described by the requirement that it must not cover the upper lip line or extend beyond specified lines. This guideline ensures a uniform and professional appearance in military settings, which is essential for maintaining discipline and standards within the ranks. The specific criteria for mustache length and styling serve to uphold the overall military image, ensuring personal grooming aligns with the expectations of the service. Adhering to these standards helps project a cohesive look among personnel, reinforcing a sense of professionalism and seriousness about the duty.