Now machines  are widely used all over the world. Why are machines so important and necessary  for us? Because they can help us to do things better and faster. A washing machine helps us to wash clothes fast. A printing machine helps us to print a lot of books, newspapers, magazines and many other things fast. Bikes, cars, trains and planes are all machines. They help us to travel faster than on foot. The computer is a wonderful machine. It was invented not long ago. It not only stores  information   but also stores numbers millions of times as fast as a scientist does. Let's study hard and try to use all kinds of machines to build China into a modern country. Machines can help us to do things better and faster, so they  _  .
are difficult to make are expensive are important but not necessary are very helpful