What should you do if something in a neighbor's home is causing harmful interference to your amateur station?
Why When a neighbor's consumer device is radiating noise into your station, the practical fix is a cooperative one: help locate the offending device (switching things off one at a time is the usual method), let your neighbor know politely that Part 15 devices must not cause harmful interference to licensed services and must stop if they do, and first verify your own station is clean and properly installed so the problem cannot be blamed on you. All three steps are part of the recommended approach, so the all-inclusive choice is correct.
Watch out Each single step is true but incomplete. In particular, leading with the rules lecture without first checking your own station or helping find the device tends to turn a technical problem into a neighbor dispute.
Interference etiquette: check yourself, help them hunt, inform politely. All three, every time.