What should you do if something in a neighbor’s home is causing harmful interference to your amateur station?

Resolving interference is a cooperative and diplomatic process. First, you must ensure your own equipment meets the standards of good amateur practice so you can be confident the problem isn't originating from a malfunction on your end. Next, work cooperatively with your neighbor to identify the source device. Politely informing them of FCC rules helps them understand that it is a regulatory issue regarding incidental device emissions, not just a personal complaint. Because all of these steps represent a comprehensive, proper approach to the problem, all the choices are correct.