哪位高手帮我改这篇英语短文,一共10个错误
In your school bags you have pencils,pens,a ruler or some books.Neither of these things grow in the field.they were all made in factories and invented someone.There have not always had pencils and pens,rulers and books Thousands years ago ,no one knew about these things,Who invented them?We do always know.There have been much thousands of inventions in the human history,Some of these inventions has changed the world,such as paper,printing and radio,and we know the inventors,And we have forgotten most of the other inventors.an example,who invented the clock,or the lock to the door?We do not know