In the 13th century , the famous Italian traveller, Marco Polo, travelled a long way to China.During his stay in China, he saw many wonderful things. One of the things he discovered was that the Chinese used paper money. In western countries, people did not use paper money until the 15th century. However, people in China began to use paper money in the 7th century . A Chinese man called Cai Lun invented  paper almost 2,000 years ago. He made it from wood. He took the wood from trees and made it into paper. He then put these pieces of paper together and made them into a book. Now paper still comes from trees. We use a lot of paper every day. If we keep on wasting so much paper, there will not be any trees left on the earth. If there are no trees, there will be no paper. Every day, people throw away about 2,800 tons  of paper in our city. It takes 17 trees to make one ton of paper.This means that we are cutting nearly 48,000 trees every day. Since it takes more than 10 years for a tree to grow, we must start using less paper now. If we don't, we will not have enough time to grow more trees to take the place of those we use for paper. So how can we save paper? We can use both sides of every piece of paper, especially when we are making notes. We can choose drinks in bottles instead of those in paper packets. We can also use cotton handkerchiefs   and not paper ones. When we go shopping, we can use fewer paper bags. If the shop assistant gives us a paper bag, we can save it and reuse it later. Everyone can help to save paper. If we all think carefully, we can help protect  trees. But we should do it now , before it is too late. People in western countries first used paper money in the  _   century.
17th 15th 13th 7th