Which of the following constitutes a Level 'D' violation?

A Level 'D' violation typically relates to serious misconduct, which can have significant implications for the individual involved. In this context, possession of alcohol while on duty is a clear breach of both safety regulations and professional conduct standards within a cadet framework. This action undermines the integrity required of cadets while they are expected to uphold discipline and responsibility.

The seriousness of possessing alcohol in a duty context not only creates a potential safety risk but also reflects poorly on the individual's commitment to the program's values. Such violations can lead to disciplinary actions due to their nature, as they pose risks to the individual's well-being and the safety of others.

The other options generally represent less severe infractions. Minor uniform violations and classroom disruptions tend to be more manageable and often result in less severe disciplinary actions. Similarly, repeated Level 'A' offenses, while potentially serious, may not reach the gravity associated with possession of alcohol while on duty in the operational context of a cadet program.