You are delivering mail and notice a customer's house door is wide open with no one visible, and the home looks unusual (mail piled up, lights off mid-day, etc.). What is the BEST action?

Mail carriers are sometimes the only person to visit a customer's home regularly, and USPS has formal wellness-check procedures (in some areas through programs like Carrier Alert) for exactly this kind of situation — elderly residents, accumulating mail, doors left open, signs of distress. The exam is testing whether you: (1) don't enter private property (you have no legal right to enter someone's home, even with good intentions); (2) take signs of concern seriously rather than just walking past; (3) escalate appropriately through USPS or emergency services rather than trying to handle it alone. 'Walking inside' is wrong — both unsafe and a property/legal issue. 'Leaving and never returning' is wrong — you would be ignoring a wellness concern. 'Taking photos' is wrong — that's not the appropriate response. The pattern: do not enter + attempt safe contact + escalate appropriately.