In your schoolbags, you may have a pencil, some kinds of pens, a ruler, and some books. None of these things grow in the fields. They were all made in factories. And, of course, they were invented by some people. There have not always been pencils or pens, a ruler and books. Thousands of years ago no one knew about these things.
Who invented them first? How did they have such clever ideas? We always don't know. There have been many thousands of inventions, large and small, in the human history. Some of these inventions have changed the world. Such as paper, printing, radio, telephone and computer, and we know the inventors. But we have forgotten most of the other inventors.
Who invented the clock, for example, or the lock to the door? We don't know. There have been thousands of inventors and we should grateful（感激的）to them for their clever ideas. Will you be one of them when you grow up?
