四大发明最有用的发明是什么,用途是什么 (用英文写一篇80词左右的作文)

指南针
The compass
As we all know,there are four important inventions in China,even in the world.They are the results of Chinese people.
But I think the compass is more important than the others.Because of it,we can know our country,our world.With the help of the compass,Christopher Columbus found the new land;with the help of it,we know that the earth is like a ball.Having the compass,we can see the earth clearly.It is the most important invention which is a tool to know more about this world.We can say that without the invention of the compass,there can not be a colourful world.
So,Ido think the compass is more important than the three.