Read the text below. For questions 21 to 25, choose the best answer: ‘Heavier than air flying machines are impossible,’ said the well-known scientist LordKelvin in 1895. Thomas Watson, the chairman of IBM in 1943, was wrong too when hesaid that he thought there would be a world market for only five or so computers. Predictions can, of course, be wrong, and it is very difficult to predict what the world willbe like in 100, 50, or even 20 years from now. But this is something that scientists andoliticians often do. They do so because they invent things and make decisions that shapethe future of the world that we live in. In the past they didn’t have to think too much about the impact that their decisions had onthe natural world. But that is now changing. An increasing number of people believe thatwe should live within the rules set by nature. In other words, they think that in a world offixed and limited resources, what is used today will not be there for our children. Wemust therefore look at each human activity and try to change it or create alternatives if itis not sustainable. The rules for this are set by nature, not by man.