Final answer:
When a supervisor says, "Leave your stuff at the door," they mean to keep personal matters out of the workplace and focus on work-related duties.
Step-by-step explanation:
When a supervisor says, "Leave your stuff at the door," they are instructing you to B) Keep personal matters confidential. This phrase typically means that employees are expected to leave personal issues, distractions, and non-work-related matters outside of the workplace to maintain a professional and focused environment. This directive aligns with maintaining a professional appearance, treating everyone with respect, focusing on work, completing tasks on time, and supporting the company's overall goals. By leaving personal matters out of the workplace, the aim is to promote productivity, minimize conflicts, and ensure effective teamwork.