When you were alone at home, someone knocked at the door. What would you do?

If you are an acquaintance, you will definitely call him by his first name or nickname until you know how to address him. If the other party says, "Hello, I'm here to collect the water fee, and check the gas pipeline and other property personnel, you should be careful. He may lie to you, but he may really come to check. There is a 50% chance that if the other person keeps silent and doesn't open the door, he will ignore it directly, or install a cat's eye door in the future.