阅读理解。 In the 13th century, the famous Indian traveller, Marco Polo, travelled a long way to China. He saw many wonderful things. One of the things he discovered was that 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 also use cotton handkerchiefs(手帕) and paper ones. When we go shopping, we can use fewer paper bags. If the shop assistant does give us a  paper  bag, we can save it and refuse (拒绝)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. 1. When he was in China, Marco Polo __________ . A. discovered Cai Lun invented paper B. learned to make paper C. saw many wonderful things D. read a lot of books 2. People in western countries first used paper money in the _________ century. A. 17th B. 15th C. 13th D. 7th 3. About ________ tons of paper are thrown away every day in our city. A. 1,700 B. 2,000 C. 2,800 D. 48,000 4. Which of the following is the way of saving paper? A. To use both sides of every piece of paper. B. To use the paper bags from shops more than once. C. To use cotton handkerchiefs and paper ones. D. All of the above. 5. Which is the best title(题目) of the passage? A. Saving paper. B. The history of paper. C. Cotton handkerchiefs back again. D. Cai Lun, the great inventor.