17. B
18.A
19.C
20.D

A robot cannot think or do things alone. People use a computer to control it. Today, robots are not very popular because they are too expensive, but they are very useful. They can help us save a lot of time and work. A robot can do the same work for 24 hours and it does not complain or get tired. In the future, scientists will design many types of intelligent robots. Their robots will be able to do many more complicated things. However, some people do not like robots. They fear that one day robots will be too powerful.