Final answer:
When witnessing a breach of security involving controlled substances, the appropriate action is to report the incident to your immediate supervisor.
Step-by-step explanation:
When witnessing a breach of security involving controlled substances, the appropriate action to take is to report the incident to your immediate supervisor (option A). This ensures that the incident is properly documented and addressed in accordance with company policies and procedures. Confronting the individual involved directly (option C) may not be the best course of action, as it can potentially escalate the situation and put your own safety at risk. Sharing the information with your colleagues for discussion (option D) should only be done after reporting the incident to your supervisor.