Do you forget to turn off the lights and heaters when you go out of a room? In 2040 it will not matter. They will turn themselves off--and on again when you return. You will choose the temperature for each room, the lighting and the humidity. A sensor will find the presence of a human (and, with luck, ignore the dog!) and turn the systems on, and when the humans leave it will turn them off again. The sensors will work through the central home computer, and they will do much more than just turn the fires and lights on and off for you. They will find faulty electrical appliances, plugs or switches, separate them so that they cannot harm anyone, and then warn you that they need repair. They will detect  fire and if you are out of the house, the computer will call the fire brigade. It will not be too difficult because the locks on the outside doors will be electronic. You will open them using your personal card--the one you use for shopping--maybe using a number known only to you. It will be impossible to lose the key, and a housebreaker will have to tamper  with the lock or with a window. It is not very difficult to make such tampering send a signal to the computer. The computer will be more than a fireman-policeman-servant. It will be an entertainer, and most of your entertainment will come right into your home. It does now, of course, but by 2040 "entertainment" will mean much more. For one thing, you will be able to take part actively, rather than just watching. Thanks to computers, in 2040 people will  _  .
have no entertainment outside replace TV with computers be controlled by computers have more fun at home