Final answer:
Article 137 of the UCMJ mandates that certain articles be explained to enlisted personnel at boot camp graduation, as this is a pivotal point in their transformation and understanding of their military responsibilities. The correct answer is A).
Step-by-step explanation:
According to Article 137 of the Uniform Code of Military Justice (UCMJ), certain articles must be explained to enlisted personnel at specific times during their military service, including when they first enlist or are inducted, upon every reenlistment and at least once every calendar year thereafter, and when they are promoted. The correct event during which the UCMJ articles should be explained, as per the question, is A) Boot camp graduation.
During boot camp, soldiers undergo a transformation process where they leave behind aspects of their civilian identity and learn to embrace their new identity as a soldier. This is partly symbolized by changes such as getting a haircut and donning a uniform. Understanding the UCMJ is crucial for their conduct and responsibilities going forward, and thus they are informed about these laws at boot camp graduation.