The fact "people can close doors" is illustrated with the story:1. We use doors to keep things outside, or inside, whatever is needed at the time.2. They can have screens in them so flying bugs can't get into our homes.3. They can be six inches thick and used in a bank vault to keep money in.4. People keep doors closed in order to safeguard their valuables.5. People who live in large cities feel safer behind locked doors.